I have two 'bestest' memories in WoW. The first was reaching the level cap on my first ever character and the second was an extra special Karazhan run.
My first memory, as said, is reaching the level cap. Now, I did get Vanilla™ but my memories of the "good old days" dont stem past level 24, seeing as TBC came out about 2 weeks after I got the game, so level 60 technically wasn't my level cap. If you get what I mean.
So I spent months and months slaving away, questing - as a protection warrior /facepalm. Tanking - as a protection warrior /cheer and just generally having a great time with my guild.
Now, going to Outland at 58 was HUGE for me. I'd had enough of Azeroth but that was due to me picking the single worse specc to level as a warrior and since then, I've always looked forward to Outland, infact, I still really really like it.
I spent around a month getting to 70 but my memory stems from the last half of 69 to 70. The officer core in Absolution back then was pretty small, as the guild wasn't too big, but the (at the time) GM, and 3 other officers decided they'd take me to some of the level 70 normal dungeons to give me a kickstart on loot and stuff.
Now back then, Abso had started to raid Kara and these guys were pretty well geared compared to me, in my quest greens/blues so I was just along for the ride but I'll remember the moment one of them went over Teamspeak, "fancy tanking for a bit?" Now, at the time, I shit myself. I was scared, this mobs hurt on the well geared people and I wasn't anywhere near their gear level but I said yes anyways and tanked the last trash and boss in Steamvaults. The support I got from the guys was amazing and it was then I knew I'd found a WoW home. (Yeah, I know - pass that sick bucket).
My second memory is from Karazhan. Infact, it was from one of the first times I led a raid. I was pretty well geared at this point and I actually knew the entire run off by heart as I'd done everything in there at least once. I'd volunteered to lead what was fondly known as "nug night" in which people that didn't usually get the chance to raid went into Kara to get a few bosses down and generally have a laugh. We'd been a bit late due to waiting for one of our healers to get their kid sorted and I had to pull in a more experienced raider but everything was going smoothly until we zoned in and found that none of the bosses were there...none but the last boss - the Prince! *legasp*
Now, only two of our raid had ever done the last boss in Kara before and I'd openly said "We'll give it a few goes but I dont think we'll get him tonight." Oh how they made me eat my words.
In a fantastic encounter, we killed him first time, with only 1 member dying, with /g cheering us on and people joining TS in excitement.
Now, looking back at this makes me a bit sad, seeing as only 2 out of 10 people in that raid are still in Absolution but only 3/10 still play but remembering TS erupt and me sitting there in stunned silence and then giving loot to guys that had only seen the first 4 bosses in there from the last boss was one of the best feelings I've had. Maybe better than getting the guild first LK kill last year, I dunno. It was different, because we were the definition of casual raiders back then. Plus, I didn't have to eat my words afterwards...