My title means that I am fabulous.
On another note, I still really wish that the temporary title from Blackwing Descent was obtainable permanently, even if it was through some long, convoluted means. I want to permanently be Pasis, Slayer of Stupid, Incompetent, and Disappointing Minions.
Thorland currently has Zookeeper. I went years without finishing off the World Safari achievement because the Minfernal in Felwood was such a rare spawn. Back in November I popped over to see if any happened to be out and was surprised to find multiple. Tamed one and that was it. I think they changed the spawn rate because they used to be super difficult to find. To add some perspective I got Eastern Kingdom Safari back in July 31, 2013. lol
I also like to use of Ironforge as this dwarf will always be a son of Ironforge. 
my main (a paladin) used Crusader for the longest time, just recently switched to Highlord.
All of my alts are either of the Alliance or of the Horde.
Cause I got ‘of the Black Harvest’ in moP and its required for any warlock I play 
even went back to thunder isle and beat up a whopping four rares to find the lost tome of the legion again so I could get green fire on this little guy. Fel might not be in style anymore but I refuse to change! its basically my bell bottoms.
“Brewmaster”, Kinda self-explanatory. And no I don’t goto meetings, thanks for the concern tho.
My Vanilla hunter uses the Lieutenant Commander title and transmog. Good times.
I use Champion of the Naaru because BC is my favorite expansion.
Working on “salty” on this alt, but getting the STV fishing in under 10 minutes is eluding me.
Hey there, I like your style 
and duh, obvious Captain title for us 
Manslayer, on all except my vanilla hunter and UD mage. who use old school pvp title, and “conservationist” respectively.
Salty, my favorite.
It was one of the few things that made me stand up and cheer when I got it cause fishing the coins out of that fountain was a trial.
‘I, Gamon, will save us!’
usually I have “The Undying” because it was hard to get.
My Demon Hunter named “Rainingblood” has the Slayer title for obvious reasons
“Servant of N’zoth”
FOR N’ZOTH!
I use “Slayer” because I am the leader of the Illidari. Yes, I still play that role in my “head RP”.
On my Horde demon hunter, I use no title. He is not the leader of the Illidari, and in fact only became a demon hunter because he failed at being a mage and wanted MOAR POWER.
On my mechagnome death knight, I use “…of the Ashen Verdict”. I could use “Deathlord” on him, but let’s be serious: there’s no way that the Ebon Blade is going to take a gnome for their leader, especially a gnome who later got upgraded.
I am the Highlord mainly because someone in BuPers hates me.
All my Warlocks have the “of the Black Harvest” title.
I really enjoyed the Black Harvest Warlock scenario which was challenging but fun.
I don’t think I will ever change my Warlock title.
I use the Insane title almost exclusively because I am proud that I had the dedication to achieve it.
That said, for the same reason I use “of the Black Harvest” on my warlock.
And just because it makes me laugh, I use the Proven Healer on my deathknight.
It’s neat to see all the reasons people use their titles, as it’s not something that I usually think about. 
I am Genie the Fabulous. 
My main uses The Horde Slayer. I like the sound of it.
I have that one on my hunter which I never play 
. I got it on Proudmoore at the time one of the highest population servers there was.
I just use the Immortal title for no other reason than it being unobtainable. I could use Hellscream’s Downfall, a cutting edge achievement that I actually earned without the help of gold or a carry, but it just seems like a lame title after so many years. It doesn’t stick.