My favorite fight is Vaelastrasz the Corrupt. The encounter was an all out DPS fest and back in 1.0 it was an encounter that you spammed everything in hopes of getting him down. I loved the rush of tackling that encounter and it was awesome to get his Burning Adrenaline debuff that would cause all of your hits to be crits for huge damage back then.
I like the 80 version of Onyxia because I always had a good laugh when somebody in a 10 man Ony would touch the eggs, Unlike 40 man Ony it should be impossible to cause such a problem but people still managed to do it and it always made me chuckle a bit.
for me the best encounter is with Sapphironi like his phase 2 whe he apply Icebolt in 3 guys of the raid an then all the crew run behind the players imprisoned by Ice Bolt to prevent Frost Breathits really really funny see this situation =]PS. again sorry my bad eng xP
My favorite has got to be the Twins from aq40 because they were still a pain in the neck at 70 and i'm sure if i went now it would still wipe a pug
Brutallus, hands down. The unique pitlord-skin (before Argaloth), the intensity of the fight - perfect.
Kael'thas Sunstrider was probably the one which made me the most nervous and the hardest strategy to learn and execute, in gameplay and players interactions between them. This encounter had the epic feeling.
Harbinger Skyriss, The arcatraz, obviously because of the hilarious Millhouse Manastorm. ^_^ "Alllright! Who ordered up an extra large can of whoop-ass?"
Naxx Classic and instructor razvious, he was an amazing fight back in the day. Forced you to use everything you had and failure was met with swift death and a possible wipe.
Ragnaros in the original Molten Core because of the rooms layout and his epic quotes. Too soon Executus...
I always got a kick out of Trial of the Champion. I love jousting in the Argent Tournament and was excited to see it as a main part of the "dungeon." Also, killing the Black Knight over and over again only to come back and say he didn't need that life/flesh/body is always hilarious.
My favorite encounter would have to be Atramedes. I love how it's unique and different using sound as a mechanic. Having a Blind dragon is awesome too, never seen that anywhere before.
I laways loved the chess match in Karazhan.I'm a chess fanatic, so it was like bringing the game to life for me.But I'm weird and tend to like the things others find boring or stupid.
My favorite encounter is Shade of Aran in Karazhan. "Flame Wreath, nobody move!"
Definitely Yogg-Saron. At the time it came out, it was one of the most difficult and fun fights to do. I loved learning the mechanics, doing the hard modes and there's just something awesome about the whole encounter. The voice acting is amazing and the bits of lore you get from the brain room are also very cool.
40man Naxx's 4horsemen. Its still the hardest encounter in the game for the specified level. Nothing will ever be close again.
Yogg. Old Gods are the best.
Kel'ThuzadNaxx in general, really. It's the epitome of what raiding should beTwin EmpsA fight that still kills 85's...pricelessKil'JaedenJust seeing the de facto leader of the Burning Legion rise out of the ground is exciting if you've been a Warcraft fan for a long time like I haveArchimondeSee above
Obsidian sanctum 3 drake’s pre nerf with no DK tank, no warlock and a shadow priest healing in the port holes (A.K.A Lazz on Elune)
I would have to say the Classic Stratholme's "TIMMY!"When I for the first time searched ppl for a Stratholme run (ahhh the good old days) and after an half an hour or so we managed to get a pug together we entered the undead crawling hellhole :) The whole dungeon was awesome but one of the best moment were when Timmy started running at us and yelling "TIMMYYY!" I almost choke on my drink out of laughter and my eyes where so soaked with tears of masocistic joy of laughter... I thought I was going to die (IRL) xD
Kara and the chess event was great!