so i just found this, and i haven’t really tested it throughly but from what i have used, it is really great. Much better than the analog sticks.
http://www.ebgames.com/product.asp?product%5Fid=802594
Looks weird, I think sticking to the normal PS2 Controllers would be better 
I think it’s a great option for playing FPS games.
I think people with good ol mouse and keyboard will still have the upper hand
Well as i said its not perfect, and it doesn’t work like you would want it to in every game, but it does work with everything, and also for the games i’ve tried it on, it works a lot better than the analog sticks. You get way better precision and control. Its really nice, lol, especially when you take down like five or six guys in a row because they can’t hit you as well : D. Its pretty sweet