A network logon password cracker.

THC Hydra
Source code: https://github.com/vanhauser-thc/thc-hydra
Website: https://www.thc.org/thc-hydra/ (Firefox gives false warning)
Open Source: yes
Target audience is small.

Reason: no alternatives found for this purpose. Perhaps Solus won't include any pentesting programs? I vote for it to have.