File this under "Time Management (Destruction Of)".
Valve is selling the Orange Box on Steam for $9.99 this weekend. If you haven't heard of it before, it combines Half Life 2 (and the expansions), Portal, and Team Fortress 2 all in one package.
I'm 250 hours into Team Fortress 2 and wishing I could stop. :| Even for the $50 I paid for Orange Box, that's the best $-per-hour value I've ever had from a game. But definitely my biggest productivity killer!