You should try to get a keyboard that doesnt jam when pressing 3 buttons simultaneously.
Well yeah, that's one of the the minimum requirements.
Also I think keyboards that register a command when you push down the button(rather than releasing) would be good for fighting games.
I've never tried a keyboard that registers the command upon release rather than press.
I was thinking a keyboard with flatter buttons might help a little with faster execution, and someone mentioned somewhere that you could replace the rubber things under the buttons with metal thingies for a better result, i think.
I'm not sure about how that works, which is why I'd appreciate it if some sort of specialist could fill me in.