Most kids in school amused themselves during class by playing games on their calculators.
I programmed instead.
Here are just a few of the things I've made in the past.
Most of them have been lost to RAM resets though
PASCAL: Given a row and position in the row, computes that term in Pascal's triangle
QUAD: Quadratic equation solver
ROTATE: Rotates one given point around another given point at a given number of degrees, returns coordinates of new point
TIME: A decently accurate stopwatch. Time was calculated by solving equations, and thus was inaccurate on older/new (and therefore slower/faster) models
FACTOR: Given a number, returned all factor pairs.
AREA: Given the number of sides and radius of a regular polygon, returns the area.
Various programs made to solve long 'plug in the numbers and solve' problems.
Useless 'for fun' things, including:
SNOW: Asterisks falling from the top of the screen to the bottom
MATRIX: Same as above, but with random digits and varying speeds
INSULT: Random insult generator
Various drawing programs