For response time/screen lag, plasmas are the best for gaming. I'd only stick with Panasonic though because they have the best anti-burn in and anti-image retention technology in their plasmas compared to say LG or Samsung.
Just know that within the first 100-200 hours of use (whatever the manufacturer recommends) you should 'break in' your plasma. That means not watching channels with static images like tickets or logos for more than a couple hours at a time. Also, when viewing 4:3 (standard def) channels, have them fill the whole screen. And on videogames, try to turn off unnecessary HUD images for your games. After the 100-200 hours though, you don't have to be so coddling to it.
If all that sounds too much to bother with, look for the 240Hz LCDs.
I've done a lot of searching on the net but I haven't found the answers that i've been looking for. I'm in the market for an HDTV, it's primary use is for gaming. Now my biggest concern is lag more then anything. I'm looking for the lowest lag time out there. But what brands and models are good for this? From what I hear plasmas are faster? Or is this just for response time and not lag time? I can't seem to find an answer on this. I'm looking for something around 40inches and around the $800-1000 mark if possible. Any help or advice would be greatly appreciated. Thank you.