Whats the dirtiest trick youve pulled on someone? cut the cable to thier aerial !

Whats the dirtiest trick youve pulled on someone? cut the cable to thier aerial or grassed them up for example

or even just turned off the gas supply from the outside box or even glued the locks up on thier car? come on lets be having you....TELL ALL

The best one I've ever heard was something a friend did.
Her husband knocked her about, so she cleaned the loo with his toothbrush.