Actually, you could also go with a Dragonnel for a mount. Draconomicon, pp151-152. In brief:
Large Dragon
HD: 6d12+6 (45hp)
Initiative: +5
Speed: 40', fly 90' (average)
AC: 16 (-1 size, +1 dex, +6 natural)
BAB/Grapple: +7/+15
Attack: Bite +9 melee (2d6+4) or claw +4 melee (1d8+2)
Full Attack: bite and two claws
Special Attacks: Roar (30' radius, DC14 will or be shaken 1d6 rounds)
Qualities: darkvision 60', immune to sleep/paralysis, low-light, scent
Saves: F6/R6/W6
Abilities: Str19, Dex13, Con12, Int6, Wis12, Cha10
Feats: ability focus (roar), alertness, improved initiative
Special: Paladins of 9th or higher level can choose a Dragonnel as a special mount, nd it gains abilities as the mount of a paladin four levels lower.
So a Paladin of Chaos or Tyranny would be able to pick one of these up just fine, without even spending feats on it. ^_^