My all time fav is Shadow Labyrinth from BC.
My fav is Karazhan :3 I really liked the atmosphere of it and my fav char from warcraft is Medivh :P
I loved End TIme, I didn't see it in the comments (:
Ulduar! Was by far the best and my most favourite instance designed by Blizz!
The old version of Stratholme.
My favourite instance has got to be deadmines, though it was better before the cata changes...
Stormstout Brewery, it was awesome fighting against monkeys, vermin, and beer monsters!
My favorite is The Vortex Pinnacle for sure.
My favorite instance is ICC. It was my first official raid and music hypnotized me ... besides his end was very dramatic for me the most epic. Those hours of planning... Those laughs with the band ... And Disbands.I remember how exciting it was to leave Arthas with no life and when you had the opportunity to get the invincible, which incidentally still has not left me :(However I also like very much Karazhan as its subject was very extensive and unusual.
Ulduar is definitely one of the best.
My favorite by far was Karazhan. Each fight was unique and I had a blast with it!
I presume raid instance counts, at least on a technicality, so Ulduar. The theming and fight variety... just unf.Just in case raids don't count though, probably.... Stratholme.
I will always love NAXXRAMAS! ^.^ if raids dont count then Drak'Tharon keep is my fave instance :)
Ulduar is my fave, running it at the time was epic :)
Firelands is too unique to not love
The Culling of Stratholme - takes back to the old days
I always loved Shattered Halls when it came out. As a hunter, multi-trapping was a must for CC in that place!
Pre-Cata Deadmines. My first instance and by far the most memorable.