Mine doesn't compare at all to IEDs or self-impalements, but I'll mention it anyway.
The worst I've had was when I messed up the rotator cuff in my left shoulder. I was playing racquetball, running full speed toward the wall to try to get to the ball in time to return it. I misjudged the distance to the wall, couldn't stop in time, and smashed my shoulder into it with the full force of 180 pounds of me behind it. There was zero perceived time between smacking into the wall and just being on the floor in pain.
It took probably 2 months to heal/regain full range of motion, and another few months after that before I really started to trust that arm again. To anyone who experiences something similar in the future, I offer this piece of advice: when the doctor asks if you can handle the pain, for the love of all that's good and sweet in the world, don't say yes. I was told to take 3 Advil every 4-6 hours and tough it out (no sling), which sucked a lot. I tried not to move my left arm at all, but of course that's very difficult to do. Some sort of "real" pain killers would have made a big difference.
You never really understand how much you use your non-dominant hand/arm until you can't.