Important distinction needs to be made here: Do you mean taking one thing with you into their home, or taking one thing out of their home?JoeNightmare said:Your breaking and entering a house but can only take 1 item, your objective is to mess with them to insanity at much as possible. What is the item?
If the former, I'd carry a tazer and rig it to their bedroom's doorknob for a fun shock every time they touch the knob.
If the latter, I'd take a single, small, key component of either their toilet or the lock mechanism on their front door. Nothing huge, but something that's really hard to find unless you know what you're doing. Hilarity would ensue.