What's the greatest prank you can think of? I personally like [url=]www.bringvictory.com[/url]. 100% Clean, but the most irritating thing you can pull on someone. Don't worry, won't screw up your computer, and it's worth watching at least once, and knowing what you're getting your friends into when you send them this.
EDIT: Just thought of a much more mean-spirited prank that was pulled on us two or three years ago; Hellgate London.
ANOTHER EDIT: Don't click if you don't want your Javascript to be hijacked for a bit. Not for computer-wrecking purposes, since I've sent several of my friends to it and it hasn't screwed anything up for them, just for screwing around with you for approximately 1-4 minutes (depends on how fast you click).

Not cool Cheese, not cool at all.

I'm with you on that one.
Should any other poor soul have clicked that link. Don't try to close it without disabling Javascript first.

DO NOT CLICK THIS LINK !! ITS A RICK ROLL!!! AND AN ANNOYING ONE!!!!!!

Greatest? Nay, but annoying, I'll give you that.

yust go to www.badgerbadgerbadger.com
or
http://www.youtube.com/watch?v=UA_ATLFxIA4 (klipp contains a streetfigher parody thats better than the whole streetfighter movie.
or
http://www.youtube.com/watch?v=rW6M8D41ZWU now this is a good song, unlike that Rickroll bull, this one needs to be spread word about, its made by some of Japan's best known comedians, this performance have even been on amerikan tv, some show kalled Kimmel show or like that..

Good use of scripts to create the endless stream of irritating popups though. [adam west batman] If only he'd used his powers for good instead of evil [/adam west batman]
I still think that the best IT prank to pull on someone is to take a screenshot of their desktop, set it as their desktop wallpaper and then delete all their desktop icons

i like that little device that turns the capslock on randomly.

I remember writing a script to do that once. My teacher was an evil bastard, that whole lesson was dedicated to writing pointless scripts that piss people off. Another good one was what I called "Poor Man's Disco", it cycled caps lock, scroll lock & num lock randomly and made the 3 keyboard lights flash like they were trying to be a disco

Hey, it's not like I didn't warn you guys that it was extremely annoying.

You made me want to beat something (or someone)with a stick.

I honestly didn't know these things and that it could possibly be used for malacious reasons. Sorry about that.

you want great prank
this is great prank after which everyone laughs
http://au.youtube.com/watch?v=so4K-bUtVHM
hijack websites are a big no.