My favoriate mounts in WoW are: Amani War Bear, Ashes of Al'ar, Reins of the Raven Lord, The Spectral Tiger and The Blye Dragonhawk.

Amani War Bear: Mission Impossible

The Amani War Bear was once available in Zul'Aman as a reward for those raid groups efficient enough to complete the timed chest event.  As the raid began, groups were presented with a countdown timer of 20 minutes.  When this timer ran out, the final boss would make a sacrifice - killing the innocent citizens of Azeroth that were held captive in various cages around the instance.  The point was, obviously, to beat the timer and free the captives, but this could only be achieved by killing all of the animal bosses (each of which had one captive associated with it).  Killing each boss would add a few precious minutes on to the timer, however this extra time became less and less the further your group advanced.  Also, each captive would grant a reward when freed and open a chest which would contain an additional epic item.  The Amani War Bear was what was contained in the fourth (and final) chest.  Unfortunately for those of us who never managed to achieve this feat (my guild would usually get 3 chests and then just fall short), this mount was retired from the game in patch 3.0, and so can no longer be obtained by anyone. 

I remember when the Amani War Bear was first introduced to the game in Patch 2.3, along with the Zul'Aman raid instance.  As my guild was only a 10-man guild, the prospect of having something other than Karazhan to run, and something that would test our skills at the same time was simply mouth watering.  Being a fan of the Troll instances, ZA became a focus of mine, and attempting it became our guild's regular Saturday night activity.  Those times hold a special place in the heart of all of our members that attended those raids, and to me, ZA was one of the most fun and challenging raids we have ever endeavored to conquer.  We did eventually down Zul'Jin - and it was a great day.  We just never quite got there in time.

Ashes of Al'ar: Mission Improbable

While Kael'thas Sunstrider's phoenix mount is still available in the game, and therefore not completely impossible to obtain, there are a lot of factors which come up against anyone seeking to get this mount.  Which is a terrible shame, because it's just so pretty.

Ever since my druid got her epic flight form back in BC, I have been absolutely champing at the bit to get my hands on these reins (please excuse the horsey puns).  Not only is it special in that not everybody can summon the boss that drops it, but it also is a rare drop, and looks amazingly cool.  Unlike a real raven it can't fly, but that doesn't matter - I have flight form anyway, which in my opinion trumps anything with a cast time.

Unlike the Ashes of Al'ar or many other mounts obtainable through raids, the Reins of the Raven Lord drops in Heroic Sethekk Halls - an instance far easier and soloable by the right class.  Being a feral druid, I have no trouble stealthing my way to Anzu's room, clearing it and then downing him on my own, and I do so almost daily.  Other classes may have more trouble trying to get it - as they will need a druid with epic flight form who is willing to take them and summon the boss, and I have seen people in trade chat paying upwards of $5k gold for this mount, should it happen to drop on one of their runs.  For me personally, the only obstacle that stands in the way of me actually getting this mount seems to be it's drop rate, or my terribly bad luck.  Not counting all the runs of Heroic Sethekk Halls I did during BC (and there were plenty - believe me), I have since run Heroic Sethekk Halls over 120 times and still not seen the Reins drop once.  I can only continue to try, in hope that tomorrow my luck will change.

The Spectral Tiger: Achievable with money

In my opinion the Spectral Tiger is, without question, the prettiest mount in the game.  When I saw it (and more recently it's cub) for the first time I unabashedly erupted into all sorts of squealy, girly expressions of delight - the kind usually reserved for really fuzzy kittens,  amazing shoes or cute things falling asleep - that eventually culminated into a big, giant "I WANT IT!".

Unfortunately my dreams of owning a Spectral Tiger were quickly dashed, once I learned how to obtain one (which was pretty quickly, since I immediately ran to the internet).  The Reins of the Spectral Tiger are obtained via a very rare loot card from the WoW Trading Card Game, and believe it or not, are currently selling on eBay for upwards of $875 - an insane price in my opinion, and one that I would never pay, but apparently other people would, and do.  If eBay isn't your thing, you could try to get one through buying booster packs - but at an average 1 card in every 484 booster packs, you'd be spending a lot more than $875 to get it that way, unless you were very, very lucky.

The Blue Dragonhawk: Achievable with time and (lots of) gold

When I first heard about the dragonhawk mounts being put in as the reward for the Mountain o' Mounts achievement, I thought it was pretty cool.  Dragonhawks had always been associated with the Horde, specifically Blood Elves, being located as mobs in and around Eversong Woods and available as their racial vanity pet.  Now the Alliance was going to be able to own one of our very own, and not only that, but it is really, really cool looking.  I can just imagine my mage flying around on the back of one of these, with her identical mini version, the Blue Dragonhawk Hatchling, running alongside. 

The Mountain o' Mounts achievement is no walk in the park, however.  Owning 100 mounts is quite the achievement, and while some people will say its easy to do - most of everyone will agree that it can be time-consuming, and costly.  If you do not already have all the required reputations, achievements, or rare drops in order to be able to get 100 mounts, start grinding now.  If you do, it's time to shell out your gold - this achievement is likely to set you back close to 50,000 gold.

Special Mention: Invincible

I just had to include Invincible's Reins here too.  Not only is owning this mount something to be very proud of - after all, you killed the Lich King and stole his horse - but it just looks amazing, doesn't it?  Blizzard has really gone to town on this guy, from the detailing on his armor to the realistic, leathery texture of his wings - it's a real work of art.  Compare it to similar styled mounts of the previous expansion, such as the Fiery Warhorse's Reins from Karazhan, and you can see just how advanced the textures on Invincible are.  Here's hoping that Invincible is a herald of things to come in terms of mounted awesomeness.

Original from mmosite.com