So I stumbled across this freeware shooter called MECHA Ritz recently and I'm pretty impressed with it. It's a bullet hell shooter with a snazzy Genesis/FM Towns-style chiptune soundtrack. It's pretty easy to simply clear despite the way it looks, but the idea with the game is to play for score and have it get harder on you as you play better.
The most striking thing to me about this particular doujin game is that it actually lets you map your own keyboard controls for once, instead of forcing ZXCV + Arrows faggotry on you.
You can download it here by clicking the big top link that says 「MECHA Ritz」 on it:
http://www.freem.ne.jp/dl/win/8513
Give it a try!
Does anon have any other underground freeware that people never seem to talk about?