Ahh man, I don't think anyone ever asked this before.
I'm sure you'll find a lot of posts here about this topic.
Generally for gaming you are looking for fast total (rise+fall) response times (16ms is a great target, but 25 ms is doable for many), good contrast ratios (400:1 or greater), and decent resolution. Match it up with a great video card and DVI and you're in.
Now, picking the size is a bit touchy. You can great gaming LCD's 17in and below, decent panels at 18-20".
I'm a bit partial to the Hitachi panels and Planar (PX 171, PX191, PL201M).