Disclaimer: First, sorry for the long rant, i just had to get it off my system. Second, i won't mention the name of the guy, there's no reason why.
That's all, keep reading :]
I normally don't get mad at newbies, in fact i pretty much laugh at their noobness most of the time, but man.. oh man, what happened today was unreal.
I get in a game (Uncreation), 1 v 2 and join the human team to make things fair. I start building a nice base with defenses tighly organized around the reactor for better protection. Then this guy just start moving the stuff around in some random places, but it's ok.. i can live with that; aliens were only stage 2 at the time anyway.
I kept playing, killed some dretches, a basilisk, got stage 2 and bought a jetpack, armor, lasgun, and ran off to the alien base to kill the Overmind (by flying over the alien base, they didn't have defenses anywhere near the door but near the om :|). And what happens when I'm running away from the marauder and jump to off the cliff to take him off me and fly? I FALL, and die! because by some weird reason the jetpack didn't work! hhhm, what happened i asked to myself? the dude decided to move the reactor 5 yards away from where it was! gah!
After the incident, i told him what had happened, and that he made me lose precious credits + a chance for us to win the game. I was tempted to leave the game, but i knew that they (an unnamedplayer had joined already) couldn't win the game by themselves.
So i started racking up some credits and bought the same stuff than before (priffle this time), because the alien base was STILL default. I took off, ready to kill them with the same ol' strategy, i managed to get to their base alive, turned on the jetpack, i was free! we had that game in our (my..) hands! ooh, i could already taste the victory [Insert Evil Laugh Here].
THEN GUESS WHAT!? he decons the f*****g reactor again!! GAH! and of course, you wouldn't expect me to live after that fall *cries*.
The whole thing was so frustrating and bizarre that i'm trying to forget it :|
At least i have the hope he understood what he did wrong at the end.. i mean, i did hear "sorry" but he didn't leave the base the whole game so who knows if he knew jetpacks don't work without a reactor

By far the worst experience i've had since i started to play Tremulous