Fairlay is a good option. It's not p2p by itself but you are indeed matching up with other people who have different opinion than you. So I guess that's P2P in a sense. It's a betting exchange which means that you can set your own odds on an event but for the bet to be valid someone else has got to be able to match your bet. Betmoose runs a similar betting exchange, you can bet on anything from politics to sports p2p.

But if you're looking for pure luck, then go for what xypos said, bitcoinrush.io. Bitdouble recently also introduced p2p coin flips i think. But looking at it right now it seems like bit double bots are the only ones that are betting so i'm not sure whether it's against the house or pvp.