I have been and always will be a fan of Stranglethorn Vale. Long questlines, huge zone, and plenty of quests make for a great time.
My favourite would probably be Hyjal, I was looking forward to seeing it for ages before Cataclysm, and it didn't disappoint. The variety of landscapes was awesome.
Thousand Needles before the shattering. I enjoy jumping from extremely high places, Noggenfogger usually saves me...usually.
My favorite zone is, well, different one, Silithus.When I heard about the event Gates of Ahn'Qiraj, i went there to see. From the very first time, i felt shivers in my spine when i saw something like a doomsday scenario with the music. and the fear grew more each step in.
Was always a fan of Un'goro Crater. Prehistoric rainforest combined with the glowing crystals everywhere made for an awesome atmosphere. Plus the cave behind Marshall's Refuge that was just filled with the crystals is still my absolute favorite spot in the game to just chill out in.
my favorite zone is barrens. only place where u can talk about the awesome chuck norris
The Storm Peaks, titan architecture along with some of my favorite questlines! Sons of Hodir unlock chain, taking down a storm giant, battling the mechano-gnomes. Great stuff.
My favourite zone has to be Vashj'ir. A lot of people don't like the fact that it is underwater but I loved the aspect of it, the fact it was unlike any other zone and the quest chain involving the Naga Battle Maiden was immense, a lot of fun. Visually it is stunning! I also loved the fact that you had a special mount just for the zone. Easily my favourite zone :)
l like badlands. the bragging quests are awesome and you get to control a full tank/heal/dps group
Zangarmash, raining everywhere all the time (i love rain), ugly things (WTF is a Sporeling? Bogstrok+Fungal giant+mushroom spore?) and BIG SHINING MUSHROOMS with Falling down GLOWING SPORES too (the best for screamshots, if with rain) *.* and my drake matchs with the place.
My favorite zone would be close between the current Stonetalon Mountains and Ulduar. Unfortunately for Stonetalon, Ulduar wins the medal. Ulduar was, in my opinion, the greatest raid Blizzard has made. It was a unique raid that involved coordination and had many unique fights. All of the content in Ulduar was released at once, unlike other large raids such as Icecrown Citadel or the Sunwell. There was no early attunement like there is/was for Molten Core, Blackwing's Lair, Naxxramas (Classic), Tempest Keep, Serpentshrine Cavern, Black Temple, Hyjal, and Karazhan. Blizzard mixed a lot of the fights with fun and coordination, making it overall a very fun raid. I don't think there will be another raid like Ulduar.
Inside Stratholme is awesome. Always been my favorite.
Once upon a time there was a place,that had extreme amounts of space,where kodos roamed wild and freeuntill a hunter came and raped them hehe,where you could go swimming in one of the five star pools,I talk about The Barrens with its chat of fools,Were raids happened daily for no reason,I guess the rogues are still in season,From the South to the North and everywhere in-between,Its no wonder why those pigs were so mean.The Barrens before the Shattering.
Redridge was always nice for me. It had a cozy town on the base of a mountain, and the burning steppes always loomed over it. the quests were fun, and i enjoyed seeing more powerful gnolls for some reason (i guess seeing gnolls stronger than hogger was entertaining?)
My favorite zone without a doubt is the Eastern Plaguelands. It's one of the most interesting questlines ever, few things are more epic than Battle of Darrowshire and feeling al the sadness around little Pamela. Not to forget about the charismatics characters we found along the road with Fiona's Caravan, geting yourself into all the pride and honor of the Argent Dawn along Gidwin and Tarenar. Really epic at all point of views.
My fav would have to be Twilight Highlands since it has a giant Sarlac Pit in it.
Un'goro Crater, for no better reason than all the old Nitendo references.
I always loved Nagrand for the art style and scenery. I remember watching my friend play in Nagrand before I was high enough level to get out there and it was a goal of mine to at least level up enough to be able to go there. I still spend time out there to this day. I just finished the rep grind for The Mag'har on my Death Knight. That, and I finished getting all the Research tokens for the two mounts from Halaa. I might actually be burned out on Nagrand for a while, haha!My favorite indoor/instanced zone is Karazhan. While it was the base level raid in Burning Crusade and nothing very impressive after T5 and T6 dominated, I still loved it and would prefer to raid there (even if I didn't need any gear).
Nagrand at night... the sky is just beautiful and relaxing. When nothing was going on, I would head out there, find myself a floating little island and just chill out and take it all in while chatting with friends.
My favorite zone would have to be the new Redridge Mountains. The Rambo questline is epic as hell and makes the entire zone so much fun compared to the snoozefest going through there was before the Cataclysm. The culmination of the chain where you drive a tank with Corporal Keeshan on the gun just blasting the hell out of everything: orcs, dragons, anything in your way.