Not a lefty, but never really played any FPS using a WASD map, always a ASDF setup. You could flip it, and go JKL; on your right hand (I would suggest doing that instead of KL;', because then your index finger can find the locating dot on the J, which is important because you'll move your fingers off to do things, like specials, and you want to return back to "home" without having to look at the keys). The S and D on my map are my strafe left and right keys, forward motion is my right mouse, primary attack is left mouse, and then I put the most commonly used needs on A (scope zoom) and F (melee attack... I play a Hunter). Everything else is just scattered in that area and I learn to go for it as I need it.