When sitting in the passenger seats of the M998 SF Gun Truck, with their weapon lowered, while holding certain guns, characters have strange twisted and folded right wrists.
This mostly occurs with vanilla and GM weapons, but some CSLA guns like the M21, Hunting Rifle, and OP-63 also cause this effect. Not that vanilla guns doing this is really OK...
It might be wise to change the sitting-with-lowered-weapon animation to have the gun pointed crosswise or vertically; this would also prevent longer guns from clipping through the seat in front of them.