Another way is to cover the ejection port with the weak hand to catch the loaded round when unloading your gun. It is possible to knock the round off the extractor and as the slide moves to the rear, the primer hits the ejector and the round explodes into your hand.
If this happens you end up with brass fragments in the palm of your hand where the tendons are. It's possible to lose much/all mobility of your fingers this way.
When we shoot IPDA stages with doorways, we try to design the stage to avoid sweeping the weak hand, on the doorknob, with the gun.
FWIW, back in November, I nearly shot my thumb off..
..with a crossbow. After a pistol match some buddies wanted me to try their crossbow. I had my thumb in the wrong place and the bowstring took most of the tip off.