...everything.
I'm decently skilled, but pretty much any human player who thinks they're good at some game could probably beat me at it. I'm either out of practice, or I react too slowly, or I don't have controls down, or I just haven't invested enough time. I'm best at a few old PC shooters where I've put in a lot of time, and at Smash Bros (friendly) once I get momentum.
My girlfriend usually beats me at Pokemon... and I'm pretty sure she tailors her team even less than I do...
Shame...