This is a huge—no, gargantuan—collection of many (maybe all?) prefabs from the long-gone site Prefab Lab.
There's about 170 prefabs here, of varying quality. Some are great, some are buggy and invalid messes. Many of the problems are probably thanks to them being stored in the
MAP format, which can't preceisely store some of the over-complicated solids some prefabs have.
Of particular note is a tank with working turret, a B17 bomber with working doors and propellers and a massive (5 garg-tall (seriously)) MechWarrior-style battle mech.
Thanks to Hunk Guerrius for the upload.