Photo credit: TurtleDiary.com
Hammer Multiplication is a fast-paced multiplication game that is similar to whack-a-mole, but without the aspect of violence. Students use a hammer, like the one that Thor is often depicted carrying, to break apart stones that have an equation and a solution that correctly match.
Disclaimer: TurtleDiary used to be free, but it looks like they are now providing some brief sample plays of their games, then charging fees.