Fives: My Favorite Mechanism

About Fives, from BoardGameGeek:

Fives is a trick-taking game for three or four players. The reverse side of the cards shows a magenta 5. The game is a must-follow game, with a fixed trump suit. In general, if you can follow suit you must, but in many cases you can play one of your cards face down as a magenta 5. However, only one magenta 5 may appear in any trick. The winner of the trick takes all cards played to the trick, with their card on top. At the end of the hand, points will be lost by any player whose top cards sum to more than 25, and points will be won for those whose cards sum to 25 or less, with the most points going to those who scored closest to 25. The player with the most points after four rounds wins.