ITT: Games /v/ didn't really play or forgot about that are great games. They must either be free or pirate-able. Try to follow the template. I'll start.

Name: Dustforce
Genre: Platformer (speedrunning)
Cost: Pirate-able
Description: You essentially control a ninja that uses a broom/mop to dust up leaves. It doesn't provide much challenge which kinda sucks, but the challenge comes from speedrunning the levels which are intense. You pick levels through a hubworld. Soundtrack is amazing.