My druid doesn't use mounts at all because flightform>Everything.
I have a random mount macro active on most of my characters which rotates between some of my favorite mounts, currently for the undead hunter (who acts as my main at the moment, if only to collect mounts) and he currently has Sunreaver Dragonhawk, a few netherdrakes, green protodrake (yeah shortly after Cata came out I got my first protodrake ever) and Tyrael's Charger. Yes I do love dragons.
Mounts I'm missing but that I really want: Red Drake, Blue Drake, Black Drake, Sandstone Drake (Vial of sands), Frostwyrm, Green Drake (why isn't that in the game Blizz?) Twilight Drake, Blue Proto-drake, Quel-dorei steed (which my undead or troll can't get because they're Alliance-only for some annoying reason. All we get is another lame hawkstrider. There's only one cool hawkstrider and that is the Swift Red one, which is a lot easier to get since its only 5 champion seals and 500 g)
I do agree with the druid flightform thing (i use it quite often as well) but I still have a couple favorite mounts, one of those is the exact dragonhawk you posted, the red drake, and the dark phoenix, as well as the rusted proto-drake(since i have been trying for nearly two months to get that thing) and my favorite thing to gripe about, as well as some other WoW forum lurkers, is the reason that a green drake is not in the game currently is because of Blizzard's choice of expansions. Simply put, why the hell couldn't they make the emerald dream expansion?!?!