Vashj'ir, short and sweet. Have only done it on my druid. Pre Cata, Desolace due to the sheer ugliness.
Orgrimmar and Stormwind.
I hear alot of ppl say Vash'jir but I honestly didn't mind the place. I would say Deepholm I don't like alot because of having to go there for the shoulder enchant on my alts, and Netherstorm it just seemed to alien or sci fi like it didn't fit in wow. OP should make this into a poll.
Silithus was just downright terrible. No zone in the history of WoW, not even old Desolace, compares to the agony that is trying to accomplish something in Silithus.
Zul'drak, troll lore /puke
in Vanilla it felt like we had 50 troll quests every other zone, a whole zone dedicated to them was just a bit too much.
Desolace is awful. Blade's Edge is like a completely copy-paste zone.
I hated Azshara, but they fixed that and I now dislike Durotar. Shocking I know its just seems very plain and shows Wow age in it, Orgrimmar & Darkspear Isle prbly the only nice parts of it.
---------- Post added 2012-04-30 at 04:20 AM ----------
Probably Darkshore for me, both pre and post cata. It feels too big and just has a really gloomy feel to it.
Zul'Drak, Old Desolace & Old Stonetalon Mountains. Fuck those harpies.
I used to like the old Silithus.
The twilight camps, getting the twilight sets to summon the mobs, the elemental invasion every few days, the packages of random crap mailed to you after the repeatable hand in, the rares scattered about the place, the lore via the Scarab chain (the red crystal especially), the elite patrols, etc. The problem with Silithus as a questing zone was that almost every single quest was a grind, but this wasn't unique to that zone by any means.
Dragonslayer Hoddie - pretending to know what I'm doing!
Silithus is just unpleasant to look at, to quest in Ive always hated that place and avoid it entirely. Well except to farm those one air mats for the low lvl agility enchant.
Zul'drak is horrible :/
I kinda love and hate this zone at the same time. Of course I'm talking about Stranglethorn Vale. Awesome place, nice quests, but try doing it pre cata, with the 40lv requirement for mounts. All this walking from the top to Booty Bay was a nightmare.