I'm playing Left 4 Dead on my XBOX360, and also returning to finish Rainbow Six Vegas, Far Cry 2 and PRG4 racing. I'm usually playing 3 or more games.
Spore on the PC, and getting bored with it. . .
see also...
http://www.badmovies.org/forum/index.php/topic,116492.0.html
Drakan the Ancient Gates on PS2. At one point I purchased a chicken - I've played the game twice already and never saw it for sale before. It was dirt cheap, and worked as a fairly powerful weapon. If you didn't mind it squawking every time you swung it. Yeah, well, apparently there's some huge stupid glitch in the game where you are no longer given missions, or the keys to get into various areas, once you've obtained the chicken. So I had to start over. Beware the chicken!