I have always rolled warlocks, but decided to try a mage.  Nothing but Horde.  I chose the UD mage for mount reasons.  The skelly horse is almost a cool a the felsteed for warlocks.  The overlooked race for mages is Blood elves, as much mana as you burn as a mage, I should have rolled a Blood Elf for the mana tap/mana torrent abilities.  But, I wanted the cool mount.