I'll avoid the really nasty ones and give a few pranks you can try on your friends.... although I can't promise they'll necessarily still be your friends afterwards!
A Day At The Office
A lot of us spend far too much of lives trapped in an office...sometimes we have to break up the monotony with a prank or two. Be careful though, you'll be working with the victims until one of you quits (unless you get yourself fired of course ;-) )!
The Flipper – a mild trick that probably won't get you into TOO much trouble, but will usually get a few laughs, and a few groans of frustration from the victim. It works on most Windows XP computers – wait for a colleague to pop off to the water cooler, then quickly go to their PC and press Ctrl-Alt-DownArrow. This will turn their screen upside down!
The confused look on their face when they return should be priceless, but make sure you help them turn it back the right way once the deed is done – Ctrl-Alt-UpArrow should put things right!
The Post-It Pandemic – a terrible waste of stationery, but usually good for a laugh. Wait for a colleague to pop out for lunch, then take every Post-It (or alternative self-adhesive note brand of your choice) pad you can lay your hands on and decorate their PC, making sure to get good coverage – there shouldn't be anything exposed once you're done. For maximum results, entirely cover their PC, desk, chair and office cubicle with a layer of Post-Its!
The Possessed PC – this one works a treat if you're sitting near to the victim and can see their screen and hand movements. When they're away, disconnect their computer mouse (but leave it on their desk) and connect yours to their PC instead. Try and mimic their mouse movements so that they think they're still in control, but then randomly move it and load things. This should confuse them! Alternatively, leave their mouse connected and connect your keyboard to their PC instead – abuse keyboard shortcuts to close windows just as fast as they can click them open, or if they load a word processor, type them a message. With a bit of luck, you'll freak them out quite nicely!
At Home (preferably not your own!)
Here's a few pranks to try at home. I've tried a few of them back in my student days, so I can vouch for their effectiveness ;-)
Toilet Trauma – a moderately nasty prank, so be sure only to try it on people you know will be ok with it. All you do is take a sheet of Cling Film (or transparent food wrap of your choice) and stretch it carefully over the toilet bowl, making sure to avoid any creases to maximise its invisibility. Put the seat down, and await the screams from the next person to use the lavatory!
Felt-Tip Facial – if one of your student buddies passes out drunk on the sofa, you owe it to them to find a set of felt-tip pens (preferably the non-toxic ones!) and decorate their face. Derogatory words, crudely drawn spectacles and moustaches, rosy red cheeks and even a full drawn-on beard are the order of the day here – let your creative juices flow! If felt tips aren't available, shaving cream beards or sliced cucumber glasses are perfectly suitable alternatives! If you're lucky, the victim won't look in a mirror before leaving the house the next day! ;-)
Shampoo Switcheroo – a nice simple one – simply empty the victim's shampoo bottle (if you're not feeling very cruel, wait for it to be near-empty anyway), and partially refill it with ketchup or mayonnaise. Head back out of the bathroom, and await the screams!
That's enough mischief for one day....do feel free to try them out on your friends, but don't blame me if they're a little less friendly afterwards...blame Loki! ;-)