Comment I'ts possible without new hardware (Score 1) 221
I'm able to grab a play station controller or a xbox controller with only my left hand and play that way. I basically learned to use the left analog with the little finger and the buttons with the thumb. The triggers are a bit tricky but many games don't need them that much. I play mostly RPG's, and turn based games but I'm able to put a good fight even in games like marvel vs capcom.
As for FPS's, I've found it easier to play in a laptop using the touchpad to aim and touch to fire. Most of the keys are reachable with the default settings but you can always use custom keyboard settings.
Just don't give up, you will get used to it in no time.