120HZ HDTV will work.
And yes i know its not a true 120hz, but they do offer a more crisp picture then a standard 60hz.
The key thing is look at response time. Anything generally under 5ms is considered gaming class.
Also id go LED with IPS, like the LG one u can find on sale.
However i heard that TV is a lotery, some come IPS, some dont.
Whhaaaat?! Please tell me you aren't *recommending* to someone who wants a gaming display device to specifically get a 120hz TV.
OP, PLEASE ignore that advice - 120hz TVs will *increase* input lag, making them worse for *all* gaming. The single purpose of 120hz on TVs is to allow better matching for 24 frame-per-second fims.
On the other hand, there are 120hz *input monitors*, which are excellent for gaming. They are usually marketed as Nvidia 3d vision monitors (3d), but can be used in non 3d mode as *true* 120hz displays.
Honestly, not to flame you aigomorla, but this is the second time I've seen you post something wildly misleading about 120hz displays, and it's pretty annoying to know there is a moderator of this site doing that. Please don't mislead the people who come to this site - it's really really annoying to see!
To answer your question OP, I currently use a 60hz TV to game, I haven't measured input lag etc, but I'd call it "fine". It's old and unavailable, so I won't even bother to tell you about it. I'm personally waiting for large format (27"+) *true 120hz input* displays to come out, then I'm upgrading.
If you are in the market for a good, low input-lag TV for gaming, I recommend searching
http://www.avsforum.com/, there are a number of excellent TVs for gaming, but as you might expect, it's tough to get good information on them.