The coffee cup crash
At one place I was working an intern lost her coffee cup.
Solution: send an e-mail with a picture of missing cup to everybody in the address book by clicking on first entry, ctrl shift End, To, then send.
Unfortunately she did not realise the address book was for the whole global corporation (about 120,000 email addresses) so the email was huge just with all the e-mails, the picture of the cup was the icing on the cake.
Result: Mail system ground to a halt for hours. Not helped by her realising her mistake and trying to fix by recalling the e-mail (3 times as this didn't seem to be working) effectively quadrupling the load on the servers.
I don't know if she got her cup back.