OPA

"27, No owls!" OPA is a trick taker where players must avoid the led suit, so as a player places a card, they might say the number of the highest card, along with the led suit which must be avoided.

"13, No bears!" If someone is lucky enough to be the only player to play a 1, they will win the trick, even though one is the lowest number. Whenever a player plays a card that is lower than the current winner of a trick, they can play it face down, so you'll never know if someone played a one, or just couldn't take the trick.

"8, No wolves!" Whenever a player wins a trick, they add a card to their tableau, trying to assemble more sets of a Wolf, a Bear, and an Owl than anyone else can before someone gets their fifth of one suit.

OPA is fairly simple to learn if you have played other trick-takers, but some of the traditional trick taking wisdom can work against a player. The game ends when any player gets their fifth of one suit, so sometimes you might want someone else to win the trick so you can win the game.
(The art on the cards is slightly different in this video.)