Ummm.... Prolly a tie between the Ceramic Pickle Christmas Ornament incident or the time me and a few friends had a buddy convinced he got some one night stand pregnant when He blacked out one night.
That puts you in the running for aM Meanie of the Week. Of course, since you're the first to answer you may not win. I guess your friend didn't break his teeth on that pickle?
I tricked a friend with fake wining lottery numbers. I had seen his ticket and I wrote down the numbers and gave them to his mother. Later in the day, he called his mom for the winning numbers and I watched him as he checked his ticket. I could see his eyes growing bigger and bigger and when he thought he won the mega millions jackpot, he whooped and hollered for about 20 minutes. He called his wife, father and a dozen other people with his "good" news. I locked myself in his car and cracked the window and told him about my sham. He was a big dude, played rugby and I thought he was going to kill me.
I was stationed in Germany when a fellow I had gone to basic training with arrived with his family. In basic training we were always paying jokes on each other so it came naturally. I told him about a set of beautiful German twin villages. One was named "Einfat and the Ousfat". (For German speakers you will note I spelled the words differently so the discussion would not turn off into another.) Well the first week end after his car arrived, which was about three months after his arrival, and I had totally forgotten what I had told him, I received a call from the Military Police stationed at an installation near the French border. He had decided to take his family for a ride and find the "Beautiful German Twin Villages". About 300 miles into it his wife had it and demanded he stop and ask directions. The Germans all gave him the same directions and he was eternally lost. Finding the US Military installation he stopped and asked the MPs. When they stopped laughing they explained the prank and he called me. You see Einfat was a word for Enter and Ousfat was a word for exit. They would be found at every entry or exit point on the German highway system.
Ancient, that's a truly wicked thing to do to a friend and raises you to the level of pranksta cum lauda.
I worked in a telecommunications hub and we still had some old teletypes left over from WWII. This particular model had an idiosyncrasy in that if you typed, in order, Figs / Blank / H it would switch off the machine. We had a new guy there one night who couldn't start the thing so we each took turns typing a few words, then the stop sequence, then handing it over to him. But the joke was on us in the finish because he got so frustrated that he stormed out of the place and went home. We had to do his work and keep the boss from finding out that he'd left.
Benedict Arnold 