Pokemon works very well for that. I've been playing Just Shapes & Beats one handed sometimes, you have to map the dash button to one of the left triggers (or the rear paddle if you have a Steam Controller like me). Great game too.
You can play Mario Kart one handed. I used to do it in Mario Kart Double Dash just to give myself an extra challenge. It's not easy, but it is kinda fun.
Strategy games would probably work well too since they are primarily mouse based. As would point and click controlled RPGs like Diablo, Torchlight, Grim Dawn, Victor Vran if you like that kind of game.
Neverwinter Nights is one of my all time favorite PC games and that is primarily controlled with mouse too. You don't even really need a keyboard, but it helps to have some things more easily accessible.
At the end of the concert she rips the foam rubber part of the microphone off and throws it into the crowd a lucky fan snatches it starts sniffing it vigorously!