Okay, well. I'm not easily embarrassed and this example isn't overly embarrassing, but some may find it so.
This summer I worked at my province's Hydro-electric plant for eight weeks with some other students who quickly became friends of mine. Between three boys and four girls, we played a lot of pranks on each other, ranging from water fights to general torture. One day, the boys thought it would be fun to tie my lunchbox to the chair with some crazy tire-ties that are impossible to cut away without a sharp knife. Well, they also tied a glass coffee-pot to the chair.
My friend Dominique and I came to lunch only to find all our belongings together, and so cursing ensued, and we attempted to hack them apart with a butter knife. Not possible, and in my attempt to step around the mess, I accidently kicked the pot with my steel-toed boot and sent it whirling across the floor in a million splintered pieces. At that time, the boys walked in to me find me standing over the mess with a very red, raged face.
Then, while trying to get my lunchbox undone, I smelled something perculiar that reminded me of our daily cleaning jobs around the plant. I opened my lunchbox to find a wet urinal cake inside!! Ahhh!! It took me a week to get rid of that smell.
My friend and I did get the boys back though, by toilet papering Earl's truck to death. I hung my bra from his antenna and wrote "Earl's gotta die" on his windshield in bright red lipstick. He drove home like that. All the mechanics came outside for a good laugh as well.
Okay, maybe that would have better suited a "practical joke" theme, but I wanted to contribute for once. :)