Maybe not the funniest but one that happened recently which I can remember.
I was playing siege as usual and recently a lot of new players had been joining in (like a month ago or something). I was defending as a low lvl scrub, so I was doing the ballista-duty and oneshotting dudes. Great fun. But as the round is wrapping up and the battle at the flag got more and more intense I pointed my ballista over there. One green newbie is (bless his kind heart) running to defend the flag. Infront of him is a heavy-armoured guy on a rooftop blocking his way. It seems it will be a short duel as the new guy charges his opponent, his overhead swing already in place well ahead of their clash. As the fated battle of the rooftop is about to happen a sudden "thud" can be heard. The well-armoured guy goes comically flying over the rooftops from the force only a shot fired by a ballista or lvl50 strength nudge can accomplish while the newcomer just stands there in awe not grasping what in the world happened. This was followed by a satisfying "HAHAH, WTF!!!? THAT DUDE JUST WENT FLYING!"
My aim had been true and the javelin pierced the heart of my foe. Continue your way to the flag, good sir.