Since I only train at home with my housemate, here are some stupid things that WE'VE done. First some lingo:
Set the beef = set the bar up with weight
Beef the set = rep that mother!
Reset the beef = unload the bar
Now we usually train together so we share the beef resetting responsibilities. But this one time I was there doing rack pulls on my own so obviously had to reset the beef on my own after I was done. So there's the bar, resting on the catchers in my rack and I begin to take the plates off one side, cue me taking off the last 20kg and, completely forgetting about the laws of physics, the 90kg or so on the other end launched my side of the barbell up faster than I could blink. My first reaction was falcoooon PUNCH, just catching the end of the bar with my knuckle an inch before destroying my face. Major ouchies ensued, with some of my skin and blood still left on the barbell. In hindsight punching the barbell out of the way probably wasn't the best move, still better than cushioning the blow with my face though.
When I first finished setting up the power rack in this house I was excited for FINALLY having somewhere to do pullups. Now, non-commercial gear isn't particularly heavy and my rack with no weight on it or anything is about 50kg so pretty easy to move around. Picture the seen, my rack is opposite my bed a few feet away with 3 friends sitting on it. I begin repping out some wide grip pull ups facing out of the powerrack towards my friends on the bed. Suddenly I feel the back of the rack lift up off the floor UH OH! and before I knew it the rack had tipped over onto the guys on the bed, but not before the middle one tried to "catch" me by grabbing my balls as I came down with the huge metal frame.