Not sure how to narrow it down to just three, but there are some that stick out more than others.
1) This happened the first time me and my guild did Molten Core back in 2006. It was a sort of collaboration with another, more experienced guild, and we were mostly there to add our numbers. There was only one problem. None of us had any significant Fire Resistance.
Predictably, we wiped. Before we even got to the first boss, we started dying in droves, and fairly soon, everybody were dead. Nobody said a thing. Then we start hearing a sound over the teamspeak (I think we used Ventrilo at the time). I don’t know if it was someone from our guild or the one we had teamed up with, but someone started laughing. And then it spread.
Within a minute of wiping, 40 people were laughing hysterically for what felt like 5 minutes and from there we ressed, went back, re-strategized and at a snail’s pace we managed to crawl our way through the place to take down a single boss. Noone was salty, nobody got angry and none of us had any regrets. That one moment was more than worth the repairbill.
2) I didn’t have a lot of self-esteem when I began playing WoW. And as a result, I didn’t have a lot of confidence in my tanking abilities and would always make excuses for why I couldn’t tank, which worked for a while when I was part of a small guild, but after we merged with a larger raid guild (the same one from the MC experience), that was no longer acceptable. I think my self-esteem issues were pretty apparent, because soon the main tank and main healer of the guild contacted me.
The main tank instructed me on how to choose my specc, allowing me a small amount of leeway to make it feel more personal and on which abilities to use, the 3 sunder rule, to always keep an eye on the healer’s health bar, to pull as few trash mobs as possible etc and then they took me to Stratholme to teach me the ins and outs of tanking in practice, little by little making sure I knew what to do and soon I was actively responding to tank requests in guild chat where before I ignored them.
It helped alot to know that even if I couldn’t see any potential in my abilities, others could, and rather than just link me to a tank guide, they took the time to dedicate weeks to making me someone who could be relied on.
3) This one is really simple. I was doing a quest in the Barrens, the objective was an Elite Quillboar. I struggled a lot to just get to him in the first place, due to all the adds between him and the nearest safe spot to eat to recover hp and when I finally got to him, I died. Many times. I was just about to give up when another player walked up to me and asked if I was on the same quest. I confirmed that I was, so we grouped up, fought our way through the adds and took down the Elite, which was still a hard fight. Deciding that we worked well together, we moved on to Thousand Needles and kept questing together for a whole day, added each other to our friends list and continued to help each other every now and then for weeks afterwards. It wasn’t anything unique. In fact, I’d wager everyone have had this experience, but it was the first time I truly fell in love with the game.