I am pretty sure Denmark allows this contest so I am commenting so yay maybe :p
I still have a lot of attachment to Utgarde Pinnacle. The Wrath dungeons were where I learned to tank, and by the end I was very good at chain pulling through them without turning it into a chaotic uncontrolled mess. UP was one of the best for that and I really felt like I had that place on complete lockdown.
My favorite instance is properly Blackrock Depths, always had quite the dungeon crawler feel to it, like some pen and paper stuff.
I absolutely love Blackwing Lair and Sunwell Plateau!
Tempest Keep is my most favorite instance!
My favorite raid instance is Ulduar, favorite dungeon instance is Well of eternity, favorite scenario instance is Battle on the high seas.
One of the most gorgeous is The Vortex PinnacleBeing a glutton for punishment, I really think I enjoyed pre-nerf Grim Batol or The Stonecore. Those were so much fun to tank!
Magisters' Terrace
My favourite instance would probably be Icecrown Citadel, a perfect end to a good expansion (aside from Ruby Sanctum).
Old Scarlet Monastery was my fav, spend hours there back in vanilla
Icecrown is, by far, my favorite instance in all of World of Warcraft
I would say Scarlet Monastery, since it's the first real instance where strategy and communication were necessary to complete it.
Auchindoun
Ulduar. Best instance ever made.
Gotta love Karazhan. Home to one of the most important figures in Warcraft Lore, with a beautiful eerie feeling to it, I can't wait you see it in the upcoming movie.
My favorite instance has to be....... Maraudon, my favorite raid instance has and always will be Karazhan.
My favorite instance would have to be the old Sunken Temple, lots of bosses, mazes, and a stone puzzle to summon one of the bosses was awesome.
My favourite instance in WoW is Ulduar. It has great lore and fantastic music I can't stop to listen! Awesome encounters and nice transmog gear ;)! Aiming for Algalon achievement with lvl 80 and only ulduar gear.
Favorite Raid (s) - Icecrown and KarazhanFavorite Instance (s) - Trial of the Champion
Magister's Terrace in dungeons, Ulduar in raids