My favorite instance is definitely Gnomergan.
I always liked Dire Maul for some reason. The differences between the wings and the novelty of having two ways to complete DM North was something new. It was a lot of fun back when you actually had to try.
My favorite instance is Grim Batol.As for Draenor i like Shadowmoon Burial Grounds very much.
Scholomance. I prefer the old version over the new one actually.
Utgarde Pinnacle for the music and Reins of the Blue Proto-Drake. Still haven't gotten that drop...
definitely deadmines and ulduar
Shattered Halls (when it was current content). I really enjoyed tanking there as a warrior and proving that paladins weren't the only option.
Pre-Cata, my answer would've been Shadowing Keep. It was awesome and it had worgen! Nowadays, it has to be Dragon Soul. Mostly because Thrall, but the fights can be fun, especially the Spine as long as people know what they're doing lol
My favorite is Shadowfang. Completes that story very well
Firelands! The mechanics of the raid were fun. Despite the panic of healing Baleroc.
The Culling of Stratholme - i've gained my passion for lore with this instance. i still run it from time to time.
FYI to those posting, the deadline for entries for the Giveaway has already passed. From the instructions above:
Azjol-NerubI loved wrath and the nerubians were so cool!
Well sure the the giveaway is already past deadline... Even so, gotta throw out there that I always thought that Blackrock Depths was an awesone dungeon (Before LFG chopped it up of course) but I really enjoyed all three of the ICC5 man dungeons as well!
always had a thing for Zul'Farrak
Absolutely Ulduar. That place has such a fantastic progression and gets so creepy at the end.
karazhan I love the music, the plot, the fights, and the visuals of this raid.