A free, industrial quality library for simulating articulated rigid body dynamics - for example ground vehicles, legged creatures, and moving objects in VR environments. It's fast, flexible & robust. Built-in collision detection.
I went to auction at a mom/pops video game store few months ago that was closing, and bought 11 slims for $200, 1 was DOA but 10 work fine. so hella deal. Already rgh3'ed 8 of them. But most younger kids don't even want anymore, unless it plays stupid "fortnight", or newer shit.