This is a fun math game that I witnessed being played while I subbed for a fifth grade class last year. I was terribly amused by it and wanted to describe it for you all. It's simply called "Buzz."
It's a great game because it helps kids practice multiples, and it's oral. You don't need anything except for the kids to sit in a circle.
All you have to do is give them a number. Let's say "7." Choose someone to go first and they will start counting with 1, next person says 2, and the next person says 3, so on and so on around the circle. The object of the game is to count quickly (have a nice rhythm going) and say "buzz" whenever you get to a number that is a multiple of the number you chose. So once they get to 14, 21 or any other multiple of 7, that person will say "buzz" and the counting continues.
If the person forgets and says the number instead of "buzz," the round ends and they have to start the counting over at 1. Counting also begins again if the person takes a long pause on their turn. The counting should be automatic. After several times around the circle, you can choose a new number.
The kids really enjoyed this game, and I did as well! What usually happens is someone doesn't pay attention and forgets they are supposed to say "buzz." Sometimes a kid won't realize a number is a multiple (especially if the counting goes on for a while and the numbers get high). When someone messes up, everyone groans and laughs and begins again. The goal is to try and keep the counting going for as long as possible, trying to beat the record for how long it can last.
This can be played with the whole class, like we did, or a small group. Give it a try!