Way back before I'd even hit level 30 I was in a game with a bunch of strangers. We were winning quite handily and having a good time (since it was a low level game most everyone was being pretty good natured about the stomp, even the enemies). I was playing Sona and my laning partner was on Ashe. We started roaming around the map just killing people at random (again, super low level so things like objectives didn't mean much).
At one point we both saw an enemy in the mid lane. We knew they didn't have flash as they'd used it earlier (i can't remember what champ it was). We snuck behind the enemy and almost simulataneously attempted to flash in and blow all of our cooldowns at once. Instead of popping the enemy like a balloon we both completely whiffed our point-blank ultimates, Ashe fired her volley in the totally wrong direction, and I misclicked my power chord onto a minion instead of the enemy champ.
The enemy champ casually walked away while our characters froze and we typed 'LOLOLOLOLOLOLOLOL' in chat about 10 times each. It was the most hilariously inept play I've ever made and it was GLORIOUS.