Dungeons of Dredmor.

binding of isaac(it is 5 right?)

IT'S A FIGHT BETWEEN THE TWO INDIE ROUGELIKES

Best game ever forever!

Also, this if you didn't see it. (re: if you're blind :P)

Alien Swarm

I remember this game as one of the best games I have ever played:

http://store.steampowered.com/app/32380/

Fortix

dungeon crawl or nethack. Free

I'd definitely recommend Dungeons of Dredmor even without the DLC.
Or if you like some old school RPGs, I'd suggest to try out Arx Fatalis or the Cthulhu saves the world pack.

TF2!

Faerie Solitaire. :)

I highly recommend Binding of Isaac

Robin Hood

Sonic CD, Puzzle Dimension, Toki Tori, and Shadowgrounds are good in their respective genres.

Sequence!

Indiana Jones and the Fate of Atlantis.

The best of the best of the best

Definitely the best $5 game i ever played.

Binding of Isaac - best singleplayer indie game what I ever played!

Black Light: Tango Down?

You should have bought Deus Ex GOTY when it was on sale Saturday for $2.99 or something like that.

bad rats the rats revenge

for me cod mw2 and payday when i buyed them from amazon for 5$ :))

The Binding of Isaac - endlessly replayable fun (and also, there's expansion coming in late april/early may which will almost double the content - cost 3$)