I like to think that I'm good at rock-paper-scissors. I bet on this game frequently with friends, and I'm well ahead lifetime. Mostly, my strategy involves talking to my opponent and more or less getting in their heads. Saying things like, "You know I'm going to throw rock. So, you probably want to throw paper." evokes some sort of response. And, over time, when playing against the same opponents, you sort of build a history of their actions and base your play on what you recall.
In the end, maybe I'm just one lucky SOB.
The NY Times put out a RPS game with a trained computer that over time exploits your weaknesses and tendencies. I played 35 rounds against it, and the nerd in me is celebrating my victory.