I don't use a numpad, but a friend of mine swears by them for playing roguelikes. It makes it much easier to move diagonally in a single turn.

If you play any games with keyboard and mouse, you could bind some letters/numbers from the right half of the keyboard and then place the macropad on the left so you don't have to take your hand off the mouse to hit anything.

For another idea, you could bind pgup/pgdn or scroll wheel up and down for scrolling webpages, IRC backlog, etc.

Hmm that's a very good use case, thanks! I'll keep it in mind for next time, I think it wouldn't have occurred to me if you hadn't said it.

Roguelikes are a great use case. I used to play Castle of the Winds all the time with a number pad, Shift+7913 fast movement FTW.

Same with MUDs: a numpad is a critical piece of kit for getting around those rooms with north/northeast/east style exits.