Worst instances of pain I can remember are:
Falling off a motorcycle going ~20 MPH in a mostly-gravel construction thing. I was mostly unharmed, except for a hairline fracture in my ankle from the bike landing on it. Hurt like hell, but I could still walk on it and whatnot. Really wasn't that bad, all things considered, but it's up there.
When I had a flat tire, was swapping it out for the spare, and as I was putting the spare on the wheel well, the jack fell over. The spare caught most of the weight, fortunately, but my hand was trapped between the spare and the wheelwell until the AAA guy showed up and used his real jack to lift the car.
That's about it for real, injury-related pain. I've had a few instances of other, minor pains, but nothing that really matches those.