If there is one thing in this game that is extraordinarily broken, its the MIT Whistles.
PREFACE: The whistles are obtained via the Stables. The best to have is Wolf + Silverback(Talbuk). The mount is summoned only for 5 minutes, it will run away once that time is up. They run close, if not exactly the speed of a normal mount. Buffs that change mounted speed DONT WORK while riding these MITs. The health for each mount is the same(IIRC its around 200k HP). They can be healed and buffed as if it was NPC, buffs applied to you such as pally bubble DONT carry over to MITs.
#1: (already posted)World PvP: These mounts allow you to cast while moving and intercept all CC you may receive so you can't be stunned or spell locked while riding!
#2: (already posted)Targeting: When people try and target you, they will automatically be redirected to your mount in training so they wont be able to report you, swapblast you, ect.
#3: Coliseum Pt 1: You can easily skip as much of the battle as you want while riding this mount, all you have to do is (while riding it) ride up to the small gate at the coliseum and resummon the same mount or another one. I've recently found the talbuk or wolf to be the best for this. Now, you wait until the game starts and use the same method to get back through the gate. *NOTE* from this point on you can ONLY summon the same mount. Trying to use other whistles WILL NOT WORK. Everyone will still be friendly once you get back over. Once you hop off the mount, you will be able to attack others and are ABLE TO BE ATTACKED so make sure to keep resummoning the mount other wise you'll fall off prematurely. *NOTE* you HAVE to hop off before the last player dies and there is only 1 left, other wise the last player is declared victorious.
#4: Coliseum Pt 2: You can use the mount to hop through the invisible wall and run around with the remaining players. Its fun to psych out DK's as much as possible
#5: (already posted) These mounts allow indoor running in draenor. You can ride them just about everywhere in draenor as long as you renew the 5 minute cool down on the mount
-If you find any other fun stuff to do with these mounts, let me know! I never tested it but I feel like you could skip the first boss of Highmaul with it by hopping through the gate and go straight to trash farming. I'd love if someone could test this for me!