ACL reconstruction. Allergic to morphine, vicadin wasn't cutting it. Eventually got demorall, and that was the greatest thing I'd ever felt.
Buddy of mine broke C2 (I think, I know it was was one of the spinal breaks you really shouldn't survive) and a few other bones in his spinal column in a diving accident, said that if given the choice between having to relive that pain and dying, just hand him a gun. The same guy had a femur fracture in a separate incident and that he couldn't even begin to compare how much worse the spinal injury hurt.
Another friend broke his back and had to hike 3 miles to get help. He was in so much pain he doesn't actually remember most of it. For my money, I'd put spinal injuries on the top of the list of most painful human experiences possible.
I once saw a woman basically get split in half by a guard rail after she got thrown from a car. Oddly enough, she seemed to be in almost no pain between the accident and loading her onto the helicopter, but according to the highway patrol report she was DOA at the hospital.