If you ever do any work in Canvas (SVG) from the bottom up, you'll end up probably using calculus somewhat for things like Bézier Curves[1]. It was one of those times I thought to myself, "I'm glad I took 4 quarters of Calculus." Knowing derivatives and such for making a game is also useful when it comes to Newton's laws and knowing acceleration is just the rate of change of velocity and velocity is the rate of change of distance.

[1] http://en.wikipedia.org/wiki/Bézier_curve