I recently have gotten really into Just Cause 2 - It's like Grand Theft Auto, except in a HUGE world, you're a CIA agent and have a grappling hook too. All-in-all I feel that it's a GTA-type game but done right.
Counter Strike: Sourse + Gmod - The Trouble In Terrorist Town mod is lots of fun.
Portal 2 - Just a fun chill game to play and maybe listen to music or whatever.
Left 4 dead 2