As far as I can see, the skills most of the time are the things that the player themselves have displayed?
Like Federer's Inside out master, he's honestly been the most terrifying inside out player for years now. Or Passing Shot Sniper, when people go to the net against him he has consistantly hit ridiculously accurate passing shots that other players just cant replicate reliably.
Or Crushing passing shot, James Blakes M.O. has always been when people are at the net, just hit it as hard as I friggin' can.[/img]