When I taught a large lower elementary, one of my favorite first year works was negative snake game. The boys, yes it was most often boys who loved this work, would stretch a row of positive and negative beads across the floor. They would then scramble along looking for ones that were opposites (+4 and -4) to remove first since they canceled each other out and the problem would be much simpler to work without all those guys. (See the history of negative numbers – cool side trip.)
Today I began working with inverses in algebra with my older kids. I realized that I should have taught the term “inverse” in the process of working with the negative snakes. We had to back fill a bit about inverse numbers and their relationship to the way positive and negative integers work in algebra problems.