My most painful in no particular order;

1. Cutting into lung tissue by the surgeon to re-inflate the lung (no anesthetic, excruciating);
2. Being stabbed in the back;
3. Being run over by a car while riding bike;
4. Laughing with broken ribs;
5. Kidney stones;
6. Ruptured appendix while vomiting blood;
7. Having root canal pain that never went away until root canal performed;
8. Vomiting and diarrhea simultaneously due to poisoned cookies at Deseret Towers;
9. Broken nose from swimmer diving into me while walking to the edge;
10. Bonking on 80 mile ride in 100 degree heat;

Those are top ten though I may have forgotten others. (Busted knee required surgery and a broken hip that I hiked to Kilimanjaro grinding the whole way before going into surgery immediately after that).