Mount up!

[vorpal blade]

A unicycle. Or a giant hamster.

[theundeadhero]

Some sort of cleverly disguised girrafe.

[Sergeant Hartman]

A horse, with the paladin upgrade

[I Took the Red Pill]

A bison.

[Nominus Experse]

My girlfriend

[Jess]

Seals! Everybody loves seals!

[oddler]

Fantasy-style? Behemoth, please.

We talkin' real deal? Jowy's got it whipped. Bear.

[Meat Puppet]

Probably some kind of 1950s luxury automobile.
If we’re going by Odd Eye’s “Fantasy-style” law, then it would be the same deal, except the car would fly. Not like in (SPOILER)Grease, though. My own would hurl like... snotVikings or something.

[Avarice-ness]

One of those Flamboyant bird mounts the Blood Elves have in WoW.

[Renmiri]

A dragon!!!

[mooglebunni608]

A kitten *mounts up and hears a squishy crunchy noise*

Uh, scratch thet, I will ride a giant watermellon

[Dr Aum]

Undoubtably I would ride a miniature Cthulhu.

[Vermachtnis]

One of those strange puppet things that Anise rides in Tales of the Abyss.
...or Ryo-Ohki.

[Shlup]

Begging to not be thwacked just makes us want to thwack you all the more.

Anyway,

[escobert]

come on and try to thwack me as I fly away on my preeeeeeety dragon! and you have your silly bitting dino poop!