I think for me it was to achive the "Friends in Even Higher Places" feat/rocket 2-person mount, because this is probably one of the most useful items I've had in WoW. Me and my friends have had great fun with it! :)
Winning the Reins of the Onyxian Drake in the BMAH (Black Market AH) wars so awsome !
Finding and taming the Ghostcrawler Spirit Beast in Cata. And yes, I named it Greg :)
The Shadowmourne chain - it was a mix of a guild effort and some fun individual challenges during boss encounters, and what an incredible effect the weapon has when it builds up! It was such a shame to hang that weapon up for cata..
Mimirons head <3 And TCG mounts even though i cant get any cause noone sells cards in my country.
Having Invincible - that would be great!
Reins of the Onyxian Drake definitely. I got outbid on one in the Black Market AH for 350k and the next day it drops after over 300 kills across 11 toons since I lost the roll the day it was released in WotLK. Now I can save the gold for a Reins of the Plagued Proto-Drake someday hopefully...
My tier 6 chest piece off Illidan! Finally completed the set I raided so long for on our first kill if the betrayer.
"The Insane" title for my part. Probably a common answer for someone who has done the achievement, but again, there are good reasons for that :)
I really want the feldrake
My greatest achieve has to be the Tamer title.. Not that it was insanely hard or anything, but more that its been the most fun thing ever happening to Wow :)
nice and sweet :D
Insane in the membrane :D
getting the mount drake of the westwind remeber the good old days going back every day to tol barad and kicking thos dailys, and for now putting my time in farming ravenlord for like about 2 months now and still no luck but still kickin it. ;)
Come on, daddy needs a new pair of....tyrael hilts?
"Yo mon imma troll Druid mon"!
My favorite accomplishment of mine was leading my guilds Herald of the Titans group back in wrath and being rewarded with Mimiron's Head for my efforts.
I always wanted a Sprite Darter Hatchling but it seemed impossible to me. This pet is the cuttest to me! I even got it tattooed on my back. *-*
I farmed for weeks for the Swift White Hawkstrider and Phoenix Hatchling pet from Magister's Terrace. The day I said "If I don't get either today, I'm going to stop coming here," BOTH items dropped. First time in a LONG time in the game I legitimately squee'd all over the place.
My favorite accomplishment was killing 25H LK before Cata release!