Teoulas on 07 September 2008
I used to play Serious Sam with my roommate. It's great for co-op play, but has no story. Try finding every secret on each stage, some of them are hilarious. There are 3 Serious Sam games (SS: First encounter, SS: Second encounter and SS 2). If you like hack 'n slash RPGs, there's quite a few of them on the PC: Diablo (1 and 2), Dungeon siege (1 and 2) and Titan Quest.
Here's a list with a few more: http://forum.osnn.net/showthread.php?p=834502
