What's the best april fool's prank/hoax you've ever pulled?

I brought a spray thing full of vinegar and told people it was Gatorade. When they wanted a drink, i sprayed vinegar at them.

that doesn’t sound very funny… =)

Maybe not the funniest…but we posted about getting a divorce on our wedding blog.
(We had just gotten married in late March.)

We crossed out all our faces in our wedding pictures
and provided information for how people could get their gifts back.

We had a disclaimer at the end of the post though.
After all, we didn’t want our respective mothers to fall over from a heart attack.

@Nimis <gasp>

When I was in Vietnam our platoon had a guy who considered himself a merry master-prankster, and over time many of us became his innocent victims.

On April 1 he had about one month to go before going home, so we had the Commo Shop generate official-looking (but totally false) incoming instructions from HQ in Long Binh regarding a new secret-level operation in Cambodia, including a list of soldiers’ names who were required to participate, and whose time of separation of duty would be extended indefinitely until the conclusion of this operation (Anticipated duration: 4 – 6 months).

Some names we made up, and (for authenticity) a few others were real guys on our compound who this guy would likely recognize. His name was put about two-thirds of the way down.

We arranged for this bogus message to be put in the middle of a bunch of real incoming ones in the Commo Shop, then had someone casually mention to ‘master-prankster’ Dudley that he might want to go over there.

Hook, line and sinker. We let poor Dudley twist in the wind, hyperventilating and glassy-eyed for maybe two hours before telling him it was just the pay-back gag he’d been asking for, for most of the past year.

To this day I’ve never seen a more relieved, emotional (and still glassy-eyed) happy face as Dudley exhibited at that moment.

I can still see it.