The Binding of isaac, certainly... Almost 150 hours and i still love that game

hands down monkey island

orcs must die, audiosurf, tribes ascend, binding of isaac, amnesia, magicka, psychonauts, terraria, company of heroes

I got borderlands GOTY for $7.50... so definitely that.

half life and cs 1.6 :D

CALL OF DOOTY MOD3RN W4RF4R3 3 COZ I CAN 360 NO SCOP FAZE FAKIE SH0T N00BZ!!11!!1!111!!

secret of the magic crystals

9 Fortix

Binding of Isaac

Half-Life, Half-Life 2 and Portal of course(I honestly can't decide between them). :D
And Portal 2 if you count sales.

Magicka, it's a lot of fun.

Sotmc, fortix

I'd go with Knights of the Old Republic. Orcs Must Die, Psychonauts, and Defense Grid are all pretty great too, though. And probably others I'm forgetting.

CS 1.6 / DOD 1.3

Space Pirate and Zombies (funny name, great game).

Under $10 - Original Price: X2: The Threat (my most played game with 400+ hours)

Under $10 - Sale Price: Sid Meier's Civilization V or Age of Empires III: Complete Collection

Unreal Tournament.

Heroes of Might and Magic V

Terraria, easily. 172 hours and still going. It's only REALLY good if you also have friends that play it, though.

cs s i got for $6 and Killing Floor bundle for $7

Best game of all time is (don't know if under $10) is CS and CS:S. I have literally spent a thousand hours play both combined. That is almost 42 days!!!!!!!!

Left 4 Dead 2 on Sale xD

The Witcher (still trying to get when I get the spare cash), Terraria (only with friends), Borderlands (you can get for like $7 now), Deus Ex 1/2, Overlord, Portal (if you missed when it was free), Uplink, ect

Dota 2 is free :D

Sale or normal price? If it's the sale one, then Deus Ex: Human Revolution (http://www.nuuvem.com.br/produto/453-deus-ex-human-revolution / R$14,99 ~ 7,42 USD) and Borderlands GOTY. Normal price there are Company of Heroes, Counter Strike, Limbo, some of the games from Total War series, The Witcher, The Longest Journey...