Throne of Tides, purely based on the fact that it's underwater
Favourite raid (as for raiding) - I guess Ulduar. But instance.. hmm... Hyjal was very beautiful.
Hmm, I think my favourite was the original Naxxramas. It was the first instance I became a full time raider in. Prior to that I'd been only a part time casual raider.
Ulduar, even though I was inactive for Wrath.
I think i'll have to say Naxxramas, loved the good old days of raiding in WotLK
Gruul's Lair because it's so short and undervalued.
If I had to choose it'd be ICC, downing the LK is always fun for me, as is the Professor Putricide... Everyone loves Prof. Putricide...
It is really a good question. I think it would be Icecrown Citadel, next to Ulduar. Both are really great raid instances.For 5-man dungeons i like Forge of Souls. The ambience is just great.
I really love Shadow Labyrinth cause of its great variety. (:
My Favorite Instance is Icecrown Citadel.
Karazhan, without a doubt.
My favorite instance in the game is Throne of Tides! It's great thinking that you are underwater.
The Vortex Pinnacle without a doubt - such grace and majesty in Skywall! The music seals the deal, it's simply overwhelmingly immersive and beautiful. Besides this, who doesn't like an instance that drops a mount (though after around 200 combined kills on Altairus, I'm starting to think the Drake of the North Wind doesn't even exist!).
Vortex Pinnacle! Such a cool place, I love the architecture and the way you fly from platform to platform.
Gotta be Naxxramas, so many different themes, and as well as that, you got to do it on two different continents. How cool was that ?
My favourite instance was the first one most of us ever saw: The Deadmines...ahhh, memories.
The new shadowfang keep -- the entire silverpine zone leading up to it, the attempted assassination on the banshee queen, and or course the dungeon itself...just brilliant.
Old Hillsbrad Foothills (H) is my favorite instance. I will always remember how awesome it felt to go back and see the lore first hand! Then running around trying to find Don Carlos to get my hands on Don Carlos' Famous Hat will always be a great memory!