Your own number system!

Im going to challenge you. Come up with an idea for your own number system and explain it here!

Rules:
It can't be just like 123
If I made it into a problem, it would have to work.
It has to be able to go up to 1000.

We had to do this for a project in class. It was actually fun, and there were some interesting systems. So I want to see what the people on DV would come up with. =)

Ooooh excellent thread!

I made one when I was about fifteen.
It was a hybrid between a 12-base system and an addtion-type system like Roman numerals.

I'll try and remember how it worked and post it later.