You might have some luck with a controller, using only a half of it, and re-mapping all controls there. Steam Controller might be great since it has touchpads. That might make some mouse-requiring games playable.

Using only keyboard, damn that’s difficult to find something, haha. I think these might work, just going by my memory: FTL, Toki Tori, Undertale, VVVVVV, Braid, Dome Keeper. Basically that kind of simple 2D games. Then almost any racing game.

You could also try some eye tracking solution, can’t help with that though.