Math Card Game Ideas

When I was reading through some blogs tonight I came across this fabulous idea for a game of war on What's the Buzz - Math Fun

Which is really funny, because while I was driving home from work tonight I was trying to come up with some new math centers (addition and subtraction) and I thought up a similar game. Remove the aces and face cards from a deck of cards, and divide the cards evenly. Each player turns over two cards; if playing addition they add them up and the student with the highest sum gets to keep them. And if playing subtraction, they subtract the smaller number from the larger one, and the student with the largest difference gets to keep all the cards. Haven't tried it yet, I plan to tomorrow I'll try to let you know how it goes....