4 ms·

I was going to propose rocks, paper and scissors, best out of 15. But that can be gamed [1]. [1] - https://www.google.de/search?q=winning+at+rocks,+papers+scis

• joneil 11y ago
  The first result suggests announcing your move, and following through, gambling that most people think you are lying. In the last 10 years I've only ever played scissors, and I usually tell people ahead of time, and I still win about half the time.