Long time back, DIY tire rotation on my Mitsu Eterna, resulting in cracking one hex nut, hence could not open! This was probably due to the tire shop tightening it too hard previously, and maybe my tools not up to std too. Ended up went to a machining shop, welded the hex key to the nut then open, but rims got burnt/melted paint in some areas near the center.
Another one just happened a few months ago on my Evo. Tried to switch battery while engine on. The positive terminals doesn't have the rubber cover and accidentally touched the strut bars hence engine shut. Forgot to take the keys out, windows was closed, then hooked up the battery and the the doors all locked! And I didn't have spare key yet! So yeah, had to pay locksmith to open up the door. Just stupid mistake.