In high school I actually made money on bets with my 57 Plymouth. I'd bet anyone I could throw it into reverse at 70mph and they couldn't in their car but they would have to try their car first if they accepted the bet. Didn't last long. Everyone soon learned my push button automatic would just go into neutral.
Reminds me of a couple of sucker bets I used to use in friendly situations.
1) Say "Take a $ bill out of your pocket, throw it up in the air, and I bet it will land face up." Most people are in the habit of stacking their bills face up and folding them in half with the face facing them. Even if you hold the bill flat face down at eye level and let go, most of the time it will land face up. Aerodynamics.
2) Let someone shuffle a deck of cards as much as they want to. Then tell them to count out 25 cards in a stack face down on the table. Bet them you can arrange those 25 unseen cards into five pat hands (Pat is defined as flush, straight, full house, or four of a kind with 10 or better). With a little practice you can do it 995 times out of 1000. It's even more amusing when you tell them to take two random cards out of the 27 that are still in their hand and offer to do it again with the 25 cards still in their hand. Or for the second bet, let them choose any 25 cards they want you to use. It's almost impossible for them to select 25 cards you can't rearrange into 5 pat hands.