Creative people help! Ideas for a plastic part to make!

[sleepydsm]

I've going to school to be a machinist, and now in Mold and Die Making class I have to... make a mold. I can't think of anything to make! I was thinking a triple diamond oil cap, or something like that. Any ideas anyone? Has to fit within about 5"x8" and use 5-6 oz. shot. So an oil cap might not be a bad idea. Any ideas would be helpful, and no sex toys haha.

Thanks!