Discovering the zones in EQ and learning how to play (first mmo I ever played). In the first few days, levels, dps and gear didn't mean shit to me, and it didn't occur to me that some creatures would be completely impossible to kill (that was very different from other games I had played up till then).
So here I go discover the world, as an intrepid lvl 3 or 4 human ranger, and end up zoning into west Karana.
I wander around (completely randomly, I had no idea there was a zone map), and see some huts. Lets go take a look ! Wait ... what's that ? A lion ? Holy crap I better go hide in one of those huts ... ok I should be safe now ... nope, the lion is hitting me through the walls.
So I started fighint back, and another player (or guard ?) arrived and killed the lion, anyways, I didn't die (yet). Night is falling, and I decide to try to find my way back to Queynos. Hmm strange, I didn't remember those hills on the way here ? Oh well, might be a shortcut ! I can't see shit because it's dark, and end up arriving at a hill giants camp. Mind you, I am being quite careful now, but their agro range was quite huge (as I recall at least ! ... but then maybe I also thought at the time that by aiming really well and shooting an arrow in one of the giant's throat, I would kill it and become a legendary hero in Queynos ! yay me for being so naive about game mechanics !).
Anyways, the giant was running much faster than I did.
So now I am back in Qeynos, naked, and no clue how I am going to find my corpse back. I find my way back to west Karana, and wander around trying to remember the path I took earlyer. After a couple minutes, I ran into a halfling druid, level 44 (god like ! I had never seen someone that uber. Picture running into someone level 4000 in wow). He cast SoW on me and some other buff, taught me about the /corpse command, had me consent him, and went to get my corpse from the hill giants, killing one in the process (with me staring in awe in the background).
That guy's name was Heppen (on Saryrn). I can't remember the name of 99% of the people from the 2 raiding guilds who I spent years playing with, but that guy, I won't forget.
I got ranger, rogue and pally epics, raided everthing in Kunark, Velious and Luclin, but compared to the first few days/weeks of discovery in this this "revolutionary" game, those other memories feel meaningless.
Also maybe the best of the best class tournaments, that was fun, with server GMs as refs, killing spectators that would not sit during fights (arenas were somekind of free for all zones I think, so if you were sitting you were unable to cast spells or interfere with the fights), and massive brawls at the end. And the winner would get a title ! Very, very few people had titles, it meant something.