New indie music game on Steam. $7.49 http://store.steampowered.com/app/49600/
I DLd it last night and it is pretty cool. The 'power' of the music determines the power of your gun and can make for some challenging situations. Warning though, it is very flashy. Doesn't bother me but ive heard other people being put off by it.
If you were ever into Audiosurf you should probably check this game out.