One card Guts. Each player puts the card on their forehead, seeing everybody's card but their own. Highest card wins.
This is not the game for everybody, due to its simplicity and lack of any relation to actual poker. It almost found its way into the Non-Poker Games section but it is typically played as a Guts game. Even the name of the game is politically incorrect. The game involves each player putting a card on their forehead, a la feather on the Native Indian headdress.
The dealer deals a single card to each player. At the same time, each player raises the card to their forehead, but not so they can see it. The card is placed face-out on their forehead so that each player can see everybody else's card but their own. There is a declare round, where each player calls "in" or "out" on the strength of everybody else's cards. Everybody who calls "in" throws their cards down. Whoever has the highest card collects the pot. Everybody else who called "in" matches the pot and the game continues.