Has to be Ragnarok Online. I played a crapton with my RL friend from school and met some good online buddies through the game too. Lots of fun, tho I can't recall a lot of particular moments.
My single favourite experience has to be the time I managed to go Metal Gear Solid during some WoE battle. It's probably way less epic than it felt for me at that time, but I'm still typing it out.
For context: for some reason me and my friend played the US international version (because it was ahead of EU servers?). Because of that (and maybe my internet being shoddy in general) all the responses to my action were pretty slow, atleast 1+ second before my character would walk or activate a skill. Doing skill combos or anything with precision was impossible for me. So I rather just click and hold the auto-attack button as a main way of attacking. Ended up becoming an "crit" Assassin class to "help break the crystal" during WoE. No skills needed, just hold down that attack button.
WoE being War of Emperium, 2 hours of PvP combat in castles in certain map locations. Damaging and eventually "breaking" the crystal inside the castle would conquer the castle for one guild (whose member got the last hit in) and teleport all non-guild members some place outside on the map. When the 2 hours period is over the current guilds keep their castles. This PvP was one of the main pulls of the game for me, but because I was playing the US server the times would be on a wednesday 3AM to 5AM and on a sunday from 6AM to 8AM. Wednesday was impossible for me, but I'd wake up on a sunday early as shit just to play the damn pvp with the guild.
Sometimes I woke up early and it turns out none of the other guild members (or ally guilds) would bother with WoE that day. Damnit, I woke up early for that shit! Well I'm awake now, might aswell walk around and do something. It's in times like these that I sneaked through the chaos of major PvP battles going on and try to sneakingly break crystals all solo (which I actually managed to do twice, ha). Assassin skills were very useful for this, Cloaking allowed me to run around invisibly, while the thief skill Hiding would make me stationary, but made me invisible and also made me invulnerable to magic AoE damage as long as I wasn't spotted. Switching between the two was pretty easy, tho other players would see your skill name being used.
With the way moving from room to room (and map to map) works in Ragnarok Online, you basically had these big glowy circles that indicated it would get you to a new location and basically had your character teleport in with a loud noise, even when it was just doors in a castle, lol. However, these teleport locations wouldn't work if you were cloaked or hidden. So guilds guarding the castle would all stand position near one of those doors, while other guilds on the "other side" would try to coordinate what they would do, who would take out what class, etc. Me on the other hand would cloak and wait alongside the attacking guild and go in with them the moment they'd run in, hoping I wouldn't immediately get wrecked by AoE magic from the defending guild. Sometimes it worked and I quickly cloaked and moved back on top of the glowy blue teleport spot that would teleport me back to the other room. There I'd hide to keep myself from getting hit by magic. By moving deep into the teleport field it was less likely any other player with a skill that would de-cloak me could catch me.
After things calmed down and the attacking guild was done away with, I sneaked past the defending guild's heavily fortified line of multiplayer players, through these very small hallways, into the next room where the crystal was completely undefended. Thought it'd be awesome if I could surprise that lot by breaking that thing under their noses... buuut, I guess they get alerted when their crystal is damaged? Two players suddenly came walking into the room as I was chipping away on that crystal and saw me. I cloaked and hid somewhere at different spots as I moved about. What followed was some goofy looking scene where a whole bunch of players came running in with a speed up buff, trying to detect me with their different detection skills, checking in old spots I just moved away from, barely missing me when rushing past me in the small hallways, etc. I somehow avoided detection even as I was switching between the crystal room and defending room to hide in. It went on long, must've run around for 15 minutes.
But after that, two players kept a constant watch over the crystal and I couldn't get near anymore. I waved /hello from the other side of a wall, they just stared me down. WoE time was also about to run out and it didn't seem like another guild was going to attack. So I sneaked back to the defending line, who seemed to be chillaxing and chatting for the most part, placed a poison bomb and had a /laugh. Then their hunter proceeded to get up and give me a face full of arrows.
So yeah, even tho most of the WoE experiences were more work and a bother to even wake up to do it than they were fun, that experience is one of my favourite online multiplayer experiences in general. Just a weirdly tense, goofy chase in a game that's not really built for it.
