Number Munchers was THE fun educational computer game while I was in elementary school.

I can't even begin to fathom how many hours I spent moving that little frog with the enormous jaws across the grid looking for tasty numbers to eat and watching the retarded "cutscenes".

The wastershed event was the day I figured out how to break into the "Administrator's Options" screen and change it so that the Prime Numbers game only had the numbers one, two, and three on the screen every round.  I was more in it for the reflexes than the math, and this allowed me to happily crunch away at the ones and threes while ignoring the twos and without worrying which new numbers were going to show up each round.  I got sufficiently good at this that by the time I would lose, the game speed (which increased each few rounds) seemed to approach the speed of light.

I'm convinced that most of the blinding reflexes I use while fencing came from this game.