I use "Homework Lotto" in my classroom as a reward for those who turn in their homework for the entire week. Students create colorful tokens with their name on it and place it on a number on the board. After lunch, I randomly choose THREE numbers using a lotto ball. If a student's token is on that number, they choose a cool "school supply" from the prize basket. Prizes are always school related: compass, fancy ruler, smelly markers, art paper, etc. If the numbered space is empty, no prize is given out. This is when they always beg me to pick another number, but you have to hold your ground. Three numbers. Three chances to win.
As the year progresses, I add suspense to the number calling. Instead of saying, "Number 13," I will call out, "It's a two digit number that is prime. Both digits add up to an even number. Both digits are also prime." They love this!