Levels/areas you know like the back of your hand

[One Pigeon]

Counter Strike's cs_assault, from altogether too many failed attempts to get in through the bloody roof.

That's funny because my abiding memory of that map was waiting just underneath the main ladder into the vents, waiting to shoot blindly into the bottom of it with my trusty AK after hearing any sound coming from inside.

[Memph]

Every L4D map, bar Cold Stream.
Q3DM6 I could still probably lap blindfolded, going backwards. Probably.
Sonic's Greenhill Zone Act 1.
The Ridge Racer track.
Most WoW dungeons :|

Aside from MP stuff, I tend not to play games to death anymore to remember every nook and cranny off the bat.

[Berzee]

I thought I'd spend some time in the toilet cubicle playing games on my android phone

I forgot to mention,
I never really wanted a smart phone until I read this post. Dangit, dangit, dangit.
(I have a company laptop but I *think* I would get suspicious looks if I always took my laptop bag into the bathroom?)