Torchlight and Torchlight 2 can be played one handed with a mouse - depending on player skill at lower difficulties or even medium, can even change a few needed buttons to whatever's easy to tap with your thumb while leaving your hand on the mouse
Breath of Death VII and Cthulhu saves the World - change the keys so they are all in one location, comfortable for you hand, and done, it's how I played, laid back, relaxed, everything set to the numpad and arrow keys
I THINK, Star Wars Knights of the Old Republic and 2 can be easily played single handed. You can pause combat at any point with a single click, attack with a single click, heal, ect. The only thing I'm not sure of would be movement but I think you can change that for ease.
X-Com - Ufo Defense, Terror From The Deep, Apocalypse, Enemy Unknown - all can be played with just the mouse with ease.
Point and Click adventure games
Many turn based games
I think Lego games can be played one handed, all you need is direction keys, attack, jump, special, and change - I play those with controllers though, so I'm not sure how easy to use with a keyboard they'd be. but, Lego Batman and Lego Batman 2 are both fun games.