Grim Fandango!
I was at Futureshop last night (I had the urge to buy something semi-useless) and found this game for $12.99! I'd never heard of it, but it looked really cool. The reviews say that the voice acting is fantastic and the visuals are really appealing. I will keep you posted about it, I haven't installed it yet. It appears to be a puzzle game like Myst and Riven. This should keep me occupied until Myst III: Exile comes out.