Wow! I am grateful I almost never crash. That's cos I'm a chicken, I'm afraid - always slow down whenever there is a slightest opportunity for any sort of problem or traffic conflict.
My last crash was about three years ago, when I was riding my then brand-new freshly bought Marin San Anselmo from a bike store. I took my left hand off the handlebars, to have a drink or something, and when I decided to put it back on the handlebar I... missed.

So instead of landing on the handlebar the hand just fell into mid-air and that caused me to lose balance. To this day I have no idea how a thing this small could throw anyone off balance... But it did me. And so there comes a spectacular crash in the middle of a perfectly paved and perfectly empty road! Luckily, the bike suffered no damage. The rider didn't do so well. I still have a small scar on my finger to remind me of this.