Some minor spills on ice or when componentry failed me (snapped pedal spindle threw me down, bizarrely snapped handlebar didn't, which was just as well as I was going about 25mph at the time - probably as I managed to slow on a controlled fashion as I rode fixed at the time).
3 biggies though (least impressive to most)....
1. Chain jumped off just as I put a spurt on to make some lights, threw me down, head/road interface was hefty. no helmet, a couple of seconds out, split head that needed 3 staples and a minor concussion. Worst was being taken to minor injuries by a colleague, forgetting his name, then forgetting my address, texting my wife to find that out, then getting called in to see the doctor as she sent me increasingly worried replies trying to find out where I was.
2. Racing, so doesn't really count probably. Training for Cycle Speedway. Thrown off by a pedal strike, and instinctively (this instinct survives no more) threw out my arm to break the fall, and broke it instead. Both sides of the elbow on my right arm, held together by pins and a big metal plate (second time I'd broken that after emulating Superman off a dining room table at 4 years of age, so I already couldn't straighten it fully.
3. Erm, broke the same arm for a third time. Damp morning, and as I approached the roudabout I thought.... Better slow down. Used by a lot of buses, so I'm assuming there was oil or diesel as well as I was down before I knew what had happened. Arm immediately didn't feel right, which the blood of the open fracture confirmed. Basically I'd landed 'perfectly' for the shock to transmit up the metal plate, and focus the energy on a single point, which snapped completely, and dragged out some of the screws of the plate (still reading?). A couple of hours of the four (I think) surgery was dedicated to saving one nerve that had been ground against the plate. Post-surgery I was assured that my old plate was old tech (8 years old) and I'd had an upgrade.
When I race now I pop a baseball soft-but-hardens-on-impact arm guard on as a bit of a mental crutch (less so when commuting now). I've got a wonderful set of x-rays now.
(arriving in hospital (by car, low priority for ambulances, which were on big call outs, so wait was going to be 2 hours), with a broken arm, and clearly perfectly coherent, first question was 'were you wearing a helmet?' So I'm a stat that yes I was wearing a helmet, and there was no head injury - the fact I didn't hit my head (not a mark on the helmet) didn't make the stats as there wasn't a box for that).