So I just finish my 1st run on tazavesh market with HM and I didnt get any drop of items on the run which makes me sad… turns out the so leah decided to drop me the cartel master gearglider and it was one of my luckiest run ever.
I do know that some people run it so many times they still didnt get any drop
I got the infinite time drake from time walking dungeons on my first ever dungeon, I assumed it was 100 percent drop on first dungeon completion.
I got Ravenlord on my first run. When the mount first got added, I prepped and read up strats since it was current level stuff. Stealthed on in, cleared room, took a while and I got Anzu down to around 1/3 or so health. I dont recall exactly but he did something you had to watch out for so I hid behind one of the alters and Anzu ended up resetting. Was gonna give up since that had taken a lot of work… but I gave it another go.
Bam, birdy mount. 
I don’t think I’ve gotten anything super good on the first run through, but I did get the Felsteel Annihilator on my 2nd attempt.
Back on Elune Server. During TBC. The day that the Magister’s Terrace Dungeon opened. 10min after the servers went live, my group entered. Cleared it. The mount dropped. I won the roll.
Fallen charger on my first kill a couple weeks ago.
Traveler’s Tundra Mammoth from the Vault in Wintergrasp. First and only time I ever fought him. The mount dropped, I rolled 100 and beat everyone for it.
Way back during Wrath, on my old account (…long story) I got Anzu to drop on maybe my third run, and my blue protodrake thing from UP to drop on my first run in a random PUG group, and I won the roll. People were…not happy with me :D.
Tonight I got both paragon cache mounts from death’s advance. It is only my 2nd cache with them (I’ve basically quit doing dailies unless they are super fast and easy early in the week for shaping fate percentage or had the transmog pieces I’ll never use anyway). Venari also gave me her mount from the 2nd cache.
Honestly a mount I’ve gotten “1st try” was the ravenlord in BC on my druid. I was the only person in the group who could even summon the boss to begin with but they were necessary to kill it and the mount dropped and I won it. Wasn’t the 1st kill by any means, but I still rode that mount around and turned lots of heads at the time (may have been the 1st on my server to get it…don’t ever recall seeing one up to that point anyway).
Nowadays I just brute force dungeon/raid mounts with my army of alts.
Not drops, but I’ve had very good luck with paragon rep and maw assault chests lately. I think I got the Night Fae assault and Ve’Nari mounts the first time through, perhaps a third also.
There are 2 mounts from that dungeon, an RNG one and a guaranteed HM one. If you got the HM one than so does every other person who has done that dungeon on hard mode.
There are maybe 6 other mounts that are pretty much a guarantee to get, the Bronze Drake, the Kara HM one (1 x mount @ 20% increasing change per person), Mecha HM (same as Kara), the two under Wymrest Temple and possible something else, so basically none of those count as “OMG FIRST RUN MOUNTS!”
Best I got was first week of 9.1, Konth and 3 others from the zone all in the first week, than I got Fallen that same week and the same day Invincible. Although Invincible has taken me donkeys years to get, I just found it great I got Fallen and Invincible on the same day.
Best though in minimal time was Ashes, took me like 20 tries total.
Wasn’t my first run, and it was on an old account but, I got a hunch that if I did ony I’d get the mount one night. Ran it, got it. Was pretty cool.
You disgust me. 
Let’s see I got the white and purple hand mount first time I killed a tormentor in the maw…if that counts at all. Wishing the fallen charger was a 100% drop though…finally find it and kill it only to get a box of grey trash that barely sells for anything. God that hurt my pride so bad… I want that mount already V_V (all of this done on my 60 druid and paladin mind you not this priest)
Reins of the Onyxian Drake
Did not even know I had it until later and then figured it must be a 100% drop. It wasn’t until I read a thread on here where folks were talking about farming it for years and not getting it that I realized it was a rare drop and I was incredibly lucky.
Anyone say Baron Rivendare’s mount and I will… I will…
It’s a damn myth, I say!!
Same!
I really thought it was 100% drop and I excitedly told my wife (who was with me) “Sweet, now we got the Fallen Charger mount!”
The salt was real because she didn’t get one.
My first and only run ever in this character at ToT. Mount from the bird boss.
I honestly don’t care about mounts much.
Did the nine and the Mount dropped. No loot so I was pretty disappointed. Someone in the raid group said congrats and I just traded it to him or her as it does not mean anything to me
I took a screenshot of two flukey mount drops.
First one is is getting the Raven Lord and White Hawkstrider same day. Second is getting both Brewfest mounts in the one keg. Haven’t had good luck like that since. 
Right click image and open in new tab to make bigger.
