Another Pinterest idea I love is the Scrabble letters one. You create different wirds with the letters. Students earn letters for things like compliments in the hallway, everyone turning in homework, etc. The teacher or students randomly pick a letter from a container. The first area covered becomes the class prize.
My students are close to a gum day snd are getting really excited. I used to use a marble jar but found that this is a much better visual for the kids.