Since we're looking at crawler tractors I thought I'd show y'all mine too.

It was built from a McDonald's Happy Meal toy (from a few years ago) of a Tonka dozer. I cut off the hood and dozer blade, then made a radiator and engine from scraps of styrene and stuff. New blade and pulley system from bits of styrene and a canopy frame of soldered up copper wire.

Total cost involved...
1 Happy Meal
2 hours of imagineering