diff --git a/src/Makefile.test.include b/src/Makefile.test.include
index 06dc59cf5c..48db60f086 100644
--- a/src/Makefile.test.include
+++ b/src/Makefile.test.include
@@ -49,6 +49,7 @@ FUZZ_TARGETS = \
   test/fuzz/key \
   test/fuzz/key_io \
   test/fuzz/key_origin_info_deserialize \
+  test/fuzz/kitchen_sink \
   test/fuzz/locale \
   test/fuzz/merkle_block_deserialize \
   test/fuzz/merkleblock \
@@ -64,13 +65,12 @@ FUZZ_TARGETS = \
   test/fuzz/parse_numbers \
   test/fuzz/parse_script \
   test/fuzz/parse_univalue \
-  test/fuzz/prevector \
   test/fuzz/partial_merkle_tree_deserialize \
   test/fuzz/partially_signed_transaction_deserialize \
   test/fuzz/pow \
   test/fuzz/prefilled_transaction_deserialize \
+  test/fuzz/prevector \
   test/fuzz/primitives_transaction \
-  test/fuzz/process_messages \
   test/fuzz/process_message \
   test/fuzz/process_message_addr \
   test/fuzz/process_message_block \
@@ -96,6 +96,7 @@ FUZZ_TARGETS = \
   test/fuzz/process_message_tx \
   test/fuzz/process_message_verack \
   test/fuzz/process_message_version \
+  test/fuzz/process_messages \
   test/fuzz/protocol \
   test/fuzz/psbt \
   test/fuzz/psbt_input_deserialize \
@@ -116,6 +117,7 @@ FUZZ_TARGETS = \
   test/fuzz/string \
   test/fuzz/strprintf \
   test/fuzz/sub_net_deserialize \
+  test/fuzz/system \
   test/fuzz/timedata \
   test/fuzz/transaction \
   test/fuzz/tx_in \
@@ -567,6 +569,12 @@ test_fuzz_key_origin_info_deserialize_LDADD = $(FUZZ_SUITE_LD_COMMON)
 test_fuzz_key_origin_info_deserialize_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
 test_fuzz_key_origin_info_deserialize_SOURCES = test/fuzz/deserialize.cpp
 
+test_fuzz_kitchen_sink_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES)
+test_fuzz_kitchen_sink_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
+test_fuzz_kitchen_sink_LDADD = $(FUZZ_SUITE_LD_COMMON)
+test_fuzz_kitchen_sink_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
+test_fuzz_kitchen_sink_SOURCES = test/fuzz/kitchen_sink.cpp
+
 test_fuzz_locale_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES)
 test_fuzz_locale_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 test_fuzz_locale_LDADD = $(FUZZ_SUITE_LD_COMMON)
@@ -969,6 +977,12 @@ test_fuzz_sub_net_deserialize_LDADD = $(FUZZ_SUITE_LD_COMMON)
 test_fuzz_sub_net_deserialize_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
 test_fuzz_sub_net_deserialize_SOURCES = test/fuzz/deserialize.cpp
 
+test_fuzz_system_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES)
+test_fuzz_system_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
+test_fuzz_system_LDADD = $(FUZZ_SUITE_LD_COMMON)
+test_fuzz_system_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
+test_fuzz_system_SOURCES = test/fuzz/system.cpp
+
 test_fuzz_timedata_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES)
 test_fuzz_timedata_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 test_fuzz_timedata_LDADD = $(FUZZ_SUITE_LD_COMMON)
diff --git a/src/test/fuzz/fees.cpp b/src/test/fuzz/fees.cpp
index 090994263e..f29acace23 100644
--- a/src/test/fuzz/fees.cpp
+++ b/src/test/fuzz/fees.cpp
@@ -8,6 +8,7 @@
 #include <test/fuzz/FuzzedDataProvider.h>
 #include <test/fuzz/fuzz.h>
 #include <test/fuzz/util.h>
+#include <util/fees.h>
 
 #include <cstdint>
 #include <string>
@@ -23,4 +24,6 @@ void test_one_input(const std::vector<uint8_t>& buffer)
         const CAmount rounded_fee = fee_filter_rounder.round(current_minimum_fee);
         assert(MoneyRange(rounded_fee));
     }
+    const FeeReason fee_reason = fuzzed_data_provider.PickValueInArray({FeeReason::NONE, FeeReason::HALF_ESTIMATE, FeeReason::FULL_ESTIMATE, FeeReason::DOUBLE_ESTIMATE, FeeReason::CONSERVATIVE, FeeReason::MEMPOOL_MIN, FeeReason::PAYTXFEE, FeeReason::FALLBACK, FeeReason::REQUIRED});
+    (void)StringForFeeReason(fee_reason);
 }
diff --git a/src/test/fuzz/integer.cpp b/src/test/fuzz/integer.cpp
index 9dbf0fcc90..d5b5ec3c9a 100644
--- a/src/test/fuzz/integer.cpp
+++ b/src/test/fuzz/integer.cpp
@@ -24,8 +24,8 @@
 #include <test/fuzz/FuzzedDataProvider.h>
 #include <test/fuzz/fuzz.h>
 #include <test/fuzz/util.h>
-#include <time.h>
 #include <uint256.h>
+#include <util/check.h>
 #include <util/moneystr.h>
 #include <util/strencodings.h>
 #include <util/string.h>
@@ -35,6 +35,7 @@
 
 #include <cassert>
 #include <chrono>
+#include <ctime>
 #include <limits>
 #include <set>
 #include <vector>
@@ -287,8 +288,12 @@ void test_one_input(const std::vector<uint8_t>& buffer)
         try {
             const uint64_t deserialized_u64 = ReadCompactSize(stream);
             assert(u64 == deserialized_u64 && stream.empty());
-        }
-        catch (const std::ios_base::failure&) {
+        } catch (const std::ios_base::failure&) {
         }
     }
+
+    try {
+        CHECK_NONFATAL(b);
+    } catch (const NonFatalCheckError&) {
+    }
 }
diff --git a/src/test/fuzz/kitchen_sink.cpp b/src/test/fuzz/kitchen_sink.cpp
new file mode 100644
index 0000000000..af6dc71322
--- /dev/null
+++ b/src/test/fuzz/kitchen_sink.cpp
@@ -0,0 +1,25 @@
+// Copyright (c) 2020 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <rpc/util.h>
+#include <test/fuzz/FuzzedDataProvider.h>
+#include <test/fuzz/fuzz.h>
+#include <test/fuzz/util.h>
+#include <util/error.h>
+
+#include <cstdint>
+#include <vector>
+
+// The fuzzing kitchen sink: Fuzzing harness for functions that need to be
+// fuzzed but a.) don't belong in any existing fuzzing harness file, and
+// b.) are not important enough to warrant their own fuzzing harness file.
+void test_one_input(const std::vector<uint8_t>& buffer)
+{
+    FuzzedDataProvider fuzzed_data_provider(buffer.data(), buffer.size());
+
+    const TransactionError transaction_error = fuzzed_data_provider.PickValueInArray<TransactionError>({TransactionError::OK, TransactionError::MISSING_INPUTS, TransactionError::ALREADY_IN_CHAIN, TransactionError::P2P_DISABLED, TransactionError::MEMPOOL_REJECTED, TransactionError::MEMPOOL_ERROR, TransactionError::INVALID_PSBT, TransactionError::PSBT_MISMATCH, TransactionError::SIGHASH_MISMATCH, TransactionError::MAX_FEE_EXCEEDED});
+    (void)JSONRPCTransactionError(transaction_error);
+    (void)RPCErrorFromTransactionError(transaction_error);
+    (void)TransactionErrorString(transaction_error);
+}
diff --git a/src/test/fuzz/parse_hd_keypath.cpp b/src/test/fuzz/parse_hd_keypath.cpp
index 9a23f4b2d4..f668ca8c48 100644
--- a/src/test/fuzz/parse_hd_keypath.cpp
+++ b/src/test/fuzz/parse_hd_keypath.cpp
@@ -2,12 +2,22 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
+#include <test/fuzz/FuzzedDataProvider.h>
 #include <test/fuzz/fuzz.h>
+#include <test/fuzz/util.h>
 #include <util/bip32.h>
 
+#include <cstdint>
+#include <vector>
+
 void test_one_input(const std::vector<uint8_t>& buffer)
 {
     const std::string keypath_str(buffer.begin(), buffer.end());
     std::vector<uint32_t> keypath;
     (void)ParseHDKeypath(keypath_str, keypath);
+
+    FuzzedDataProvider fuzzed_data_provider(buffer.data(), buffer.size());
+    const std::vector<uint32_t> random_keypath = ConsumeRandomLengthIntegralVector<uint32_t>(fuzzed_data_provider);
+    (void)FormatHDKeypath(random_keypath);
+    (void)WriteHDKeypath(random_keypath);
 }
diff --git a/src/test/fuzz/string.cpp b/src/test/fuzz/string.cpp
index 3de0cf8db7..49bee0e81f 100644
--- a/src/test/fuzz/string.cpp
+++ b/src/test/fuzz/string.cpp
@@ -115,4 +115,8 @@ void test_one_input(const std::vector<uint8_t>& buffer)
         assert(data_stream.empty());
         assert(deserialized_string == random_string_1);
     }
+    {
+        int64_t amount_out;
+        (void)ParseFixedPoint(random_string_1, fuzzed_data_provider.ConsumeIntegralInRange<int>(0, 1024), &amount_out);
+    }
 }
diff --git a/src/test/fuzz/system.cpp b/src/test/fuzz/system.cpp
new file mode 100644
index 0000000000..7f378c2b13
--- /dev/null
+++ b/src/test/fuzz/system.cpp
@@ -0,0 +1,123 @@
+// Copyright (c) 2020 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <test/fuzz/FuzzedDataProvider.h>
+#include <test/fuzz/fuzz.h>
+#include <test/fuzz/util.h>
+#include <util/system.h>
+
+#include <cstdint>
+#include <string>
+#include <vector>
+
+namespace {
+std::string GetArgumentName(const std::string& name)
+{
+    size_t idx = name.find('=');
+    if (idx == std::string::npos) {
+        idx = name.size();
+    }
+    return name.substr(0, idx);
+}
+} // namespace
+
+void test_one_input(const std::vector<uint8_t>& buffer)
+{
+    FuzzedDataProvider fuzzed_data_provider(buffer.data(), buffer.size());
+    ArgsManager args_manager{};
+
+    if (fuzzed_data_provider.ConsumeBool()) {
+        SetupHelpOptions(args_manager);
+    }
+
+    while (fuzzed_data_provider.ConsumeBool()) {
+        switch (fuzzed_data_provider.ConsumeIntegralInRange<int>(0, 7)) {
+        case 0: {
+            args_manager.SelectConfigNetwork(fuzzed_data_provider.ConsumeRandomLengthString(16));
+            break;
+        }
+        case 1: {
+            args_manager.SoftSetArg(fuzzed_data_provider.ConsumeRandomLengthString(16), fuzzed_data_provider.ConsumeRandomLengthString(16));
+            break;
+        }
+        case 2: {
+            args_manager.ForceSetArg(fuzzed_data_provider.ConsumeRandomLengthString(16), fuzzed_data_provider.ConsumeRandomLengthString(16));
+            break;
+        }
+        case 3: {
+            args_manager.SoftSetBoolArg(fuzzed_data_provider.ConsumeRandomLengthString(16), fuzzed_data_provider.ConsumeBool());
+            break;
+        }
+        case 4: {
+            const OptionsCategory options_category = fuzzed_data_provider.PickValueInArray<OptionsCategory>({OptionsCategory::OPTIONS, OptionsCategory::CONNECTION, OptionsCategory::WALLET, OptionsCategory::WALLET_DEBUG_TEST, OptionsCategory::ZMQ, OptionsCategory::DEBUG_TEST, OptionsCategory::CHAINPARAMS, OptionsCategory::NODE_RELAY, OptionsCategory::BLOCK_CREATION, OptionsCategory::RPC, OptionsCategory::GUI, OptionsCategory::COMMANDS, OptionsCategory::REGISTER_COMMANDS, OptionsCategory::HIDDEN});
+            // Avoid hitting:
+            // util/system.cpp:425: void ArgsManager::AddArg(const std::string &, const std::string &, unsigned int, const OptionsCategory &): Assertion `ret.second' failed.
+            const std::string argument_name = GetArgumentName(fuzzed_data_provider.ConsumeRandomLengthString(16));
+            if (args_manager.GetArgFlags(argument_name) != nullopt) {
+                break;
+            }
+            args_manager.AddArg(argument_name, fuzzed_data_provider.ConsumeRandomLengthString(16), fuzzed_data_provider.ConsumeIntegral<unsigned int>(), options_category);
+            break;
+        }
+        case 5: {
+            // Avoid hitting:
+            // util/system.cpp:425: void ArgsManager::AddArg(const std::string &, const std::string &, unsigned int, const OptionsCategory &): Assertion `ret.second' failed.
+            const std::vector<std::string> names = ConsumeRandomLengthStringVector(fuzzed_data_provider);
+            std::vector<std::string> hidden_arguments;
+            for (const std::string& name : names) {
+                const std::string hidden_argument = GetArgumentName(name);
+                if (args_manager.GetArgFlags(hidden_argument) != nullopt) {
+                    continue;
+                }
+                if (std::find(hidden_arguments.begin(), hidden_arguments.end(), hidden_argument) != hidden_arguments.end()) {
+                    continue;
+                }
+                hidden_arguments.push_back(hidden_argument);
+            }
+            args_manager.AddHiddenArgs(hidden_arguments);
+            break;
+        }
+        case 6: {
+            args_manager.ClearArgs();
+            break;
+        }
+        case 7: {
+            const std::vector<std::string> random_arguments = ConsumeRandomLengthStringVector(fuzzed_data_provider);
+            std::vector<const char*> argv;
+            argv.resize(random_arguments.size());
+            for (const std::string& random_argument : random_arguments) {
+                argv.push_back(random_argument.c_str());
+            }
+            try {
+                std::string error;
+                (void)args_manager.ParseParameters(argv.size(), argv.data(), error);
+            } catch (const std::logic_error&) {
+            }
+            break;
+        }
+        }
+    }
+
+    const std::string s1 = fuzzed_data_provider.ConsumeRandomLengthString(16);
+    const std::string s2 = fuzzed_data_provider.ConsumeRandomLengthString(16);
+    const int64_t i64 = fuzzed_data_provider.ConsumeIntegral<int64_t>();
+    const bool b = fuzzed_data_provider.ConsumeBool();
+
+    (void)args_manager.GetArg(s1, i64);
+    (void)args_manager.GetArg(s1, s2);
+    (void)args_manager.GetArgFlags(s1);
+    (void)args_manager.GetArgs(s1);
+    (void)args_manager.GetBoolArg(s1, b);
+    try {
+        (void)args_manager.GetChainName();
+    } catch (const std::runtime_error&) {
+    }
+    (void)args_manager.GetHelpMessage();
+    (void)args_manager.GetUnrecognizedSections();
+    (void)args_manager.GetUnsuitableSectionOnlyArgs();
+    (void)args_manager.IsArgNegated(s1);
+    (void)args_manager.IsArgSet(s1);
+
+    (void)HelpRequested(args_manager);
+}