Rock, paper, scissors
Do not ask us why, but if you want to win any game of ‘rock, paper, scissors, try asking a random question before the game starts. After you ask the question, the vast majority of the time the other person will use scissors. You can try it over and over again and probably get the same results.
Mind you this person will definitely catch on in a short amount of time, but you will have won a few rounds before then. We are not sure what winning at this small game might get you, but try putting some money on the line, it may work in your favor.