Orgish.com has video (2.8 Meg) of a cop shooting himself in the foot during a "don't play with guns" lecture to a crowded room. I'm not sure if it's authentic, but the man in the video wears a shirt marked "POLICE" on the front and "DEA" on the back. He is lecturing the room full of men, women, and children about "gun safety" and holds up his police-issue .40 caliber Glock-22 pistol. That the crowd is so diverse (with women and very young children) leads me to believe that it's more of an anti-gun "guns are evil, never touch them" type lecture than it is about actual gun safety.

The officer takes his gun out of the holster, and parades around with the action open. He inspects it, declares that it is unloaded, and appears to show it to someone else for confirmation. He then closes the action (which probably loaded a round from the magazine) and parades around the room with his finger squarely on the trigger. Just as he professes to be the "only one in the room professional enough. . .to carry this Glock .40", BANG he shoots himself in the pinky toe. Not to be dissuaded, he then proceeds to limp around the room and lecture everyone to not do what he did.

The crowd becomes visibly (and understandably) upset when he produces what appears to be an AR-15 or M-16 scary-evil-looking "assault weapon". As he tells the fleeing people to calm down and that he "swears it's unloaded" you can hear people yelling "put it down, put it down".

The poor guy appears to be alright although he's gonna limp for a while. Most notably, the officer broke several gun safety rules like having ammunition in the room, having a magazine in the pistol, having his finger on the trigger, and not keeping the gun pointed in a safe direction.

UPDATE: Minute of Angle has more, with a news blurb about it as well. (Apparently this happened last spring.)

The agent emptied the gun of ammunition as he pointed it toward the floor, but when he released the slide it fired into his thigh.

That is called slamfire, and I don't think that's what happened. Looking at the video, he released the slide long before he fired the round. There is no doubt in my mind that he had his finger on the trigger of this 'empty' gun.

UPDATE: Of course the whole reason for blaming the incident on slamfire is to shift blame from the officer to the gun. But even if it had been due to slamfire, if you keep the gun pointed in a safe direction and unload it properly for 'safety' demonstrations, it's not a problem.