My favorite would definitely have to be ICC. I loved so many of the fights in there, especially getting to be a vampire :) so much fun!B
Hands down to Ulduar^^ Best Boss Design and Enviroment Design ever
Still a fan of Karazhan
Hmm, I would have to go with black temple. Fond days of getting lost.
My favorite instance is Karazhan
Icecrown Citadel. It was my first step into progression raiding, and I found a guild and a bunch of new friends.
Vortex Pinnacle followed by Karazhan.
i have to admit this contest was not open long, closed on the 17th and people are still posting.So here goes nothing...Naxxramas!
Black Temple! So many girls in there...
Throne of Thunder and Dragon Soul
Gate of the Setting Sun. This was also my favorite Challenge Mode to do.
I've always loved Sunwell Plateau! i run it still because it loved the style and bosses.
My favorite was/is Zul Farak! Love the troll zombies :)
Deadmines pre-Cata. R.I.P. Mr. Smite 2004-2010.
Grimrail Depot (On the train portion of it), ten outta ten dungeon.
Siege of Orgrimmar
Karazhan hands down. The ghostly dining hall and the plays are still some of my favorite settings. Creepily classy :)