Good tools made by others

Topera

IPv6 analysis tool, with the particularity that their attacks can't be detected by Snort
HammerDB
HammerDB is an open source database load testing and benchmarking tool for Oracle, SQL Server, TimesTen, PostgreSQL, Greenplum, Postgres Plus Advanced Server, MySQL and Redis
clumsy
clumsy makes your network condition on Windows significantly worse, but in a managed and interactive manner.
WinAppDbg
Very good Windows application debugger engine written in Python.
lime-forensics
LiMe is Loadable Kernel Module, which allows the acquisition of volatile memory.
american-fuzzy-lop
Practical instrumentation-driven fuzzer for binary fileformats.