LOL well since you asked. My one fish was very territorial and would bash himself into anything that was in the tank, including the lid.. I had to put weights on top of it because one night he jumped out..
I had an electric water heater in the tank which at the time was just a glass tube, similar to a light bulb. The fish decided he didn't like that and he broke it.
When I went to take it out of the water, I got shocked so hard, it blew me backwards on to the floor. I had experienced little hits from electrical outlets and stuff before but this one was insanely out of my realm. It literally knocked me on my back as soon as I stuck my hand in the water.
I couldn't believe that the fish weren't fried but I was later told that there is no ground in the water so from me standing there and being grounded outside, I took a serious hit. LOL At least I was smart enough to unplug the heater before I managed to get it out again.
Serious lesson learned. I'm lucky I didn't kill myself.