Repost, but relevant I guess.
Really Rubbish Job.
I used to work for a nasty retail chain in Scotland, the managers there always adopted the "I am much too important for this" attitude when dealing with the staff, and working conditions there were hell.

I had handed in my notice (I was fed up with the abuse from managers and customers) and on my last day, a few minutes before the end of my shift, I decided to get my revenge on those evil managers.

Every receipt printed there has a promotional message on it, usually some shit about special offers and such, I logged into a terminal (only one user name and password, everyone used) and accessed this data, I changed it so that every receipt had the words "The managers in Makro are Fucking Wankers"

It was hilarious, as apparently it took them three days to notice it, and hundreds of receipts had been printed, Imagine if you had just bought something from them, and noticed that printed on the receipt!
( Squiggy Alloria makes theme parks., Fri 11 May 2012, 11:30, Reply)