I visited a colleague at home recently and as I was going to be meeting his six year old son Pi, I created a small model for him and took it along as a gift.
Although I modelled it from scratch to look like the name Pi when stood on its end, I took inspiration from madscifi's excellent Tiny Toy Dump Truck http://www.thingiverse.com/thing:9710
As it is apparently PI day tomorrow, I thought that others might like a copy.
It prints in about an hour with no assembly required.
So far, I've printed it a Makerware "Low" which is 0.3mm, 2 shells, 10% infill, 90mm/s, NO SUPPORT, no raft.