Useful for special characters sometimes, like alt + 0128 - €, alt + 0163 - £, alt + 0254 - þ (like a tongue sticking out in a smiley :þ).
Also people should use control + x and control + c and control + v/shift + insert with the arrow keys all the time for cut, copy and paste, they're way faster. And use tab a lot more as well. I couldn't tell you how I know people don't use them enough.... >_>
Here's an interesting math question: Why does (1/1)^2 (1/2)^2 + (1/3)^2 + (1/4)^2 + ..... equal pi^2/6.
Euler solved this age-old problem at the age of 28, and rose to international fame as a mathematician.
http://en.wikipedia.org/wiki/Basel_problem
There are lots of problems like this in Professor Stewart's Cabinet of Mathematical Curiosities 1 and 2.
For example did you know how many different colours are required to colour a map of regions so that no two regions with the same colour are touching? The answer is four.
http://en.wikipedia.org/wiki/Four_color_theorem