Many of the 17" LCDs these days are very decent for gaming. The native resolutions tend to be 1280x1024, with high contrast ratios (500:1 to 700:1), with 16ms total response times (rise+fall). Add DVI inputs and brightness levels and you have a good combo for gamin.
Many 18 and 19 inch LCD have the same resolution, but inferior response times (around 25 ms total), which does very well with gaming, but not as good as the 16ms, smaller LCDs.
The big boys, 20" and beyond, often have greater native resolutions at 1600x1200 with 25ms response times or greater. These panels are also very nice for gaming, but again not as fluid as the smaller/fast panels. There are a host of great panels out there.
In the 17" venue take a look at the Hitachi CML174, Planar PX171, Samsung 172T.
In the 18-19" take a look at the NEC models, Planar PX191, as well as the Samsung 191T or 192T.
In the 20+" take a look at the Planar PL201M, Samsung 213T, NEC 2080UX.
Go for high contrast ratios, fast response times, DVI, and match with a powerful graphics card. !