Add Mari0. That Portal/Mario crossover is the shit.
Also, for rhythm how about Stepmania?It's already in the second post.
http://www.kongregate.com/games/2DArray/you-find-yourself-in-a-roomwow, such a great game, nice find
This is a fantastic text based game that makes you reflect on, and ultimately hate your life. It's purely text based but it is almost scary, play it, you'll know what i mean.
Maybe you should read the thread before offering suggestions. Eversion has already been mentioned.Are all the games in the OP? I can see why people are too lazy to