Of what, the types, or characters?
I'd have to say Power/Bunny.
I've tried:
Dragon - Got bored of mine, skill build I was following was really boring...I only have Mana Arrow(with arrow rush) and like cure...at base level 70.
Raccoon - Quit mine around 25...no point, I was doing a pure AP, and I deleted him after I made my bunny.
Fox - I have a 31 Fox, and it just doesn't interest me to much.
Lion - My Lion is around early 20's, and it too doesn't interest me.
Sheep - Currently working on a low leveled Sheep, but I don't play Trickster to much, and its almost the same as my Dragon, for now anyhow.
Bunny - My favorite, my main, level 103. They are kind of boring, as Bunnies don't seem to have many skills, but to me, I have the most fun with my Bunny.
Which leaves Cat and Buffalo untried.
I see no point in me making a cat, because it would be the same as my bunny, if I did. a 4114 Pure AP.
As for a Buffalo, I hear their second job skills are more mob-esque, while bunnies are more like 1v1 with their skills.
Well, to reiterate, I prefer my Bunny.
Bunnies are also pretty basic.
Pure AP...all you gotta do is attack, until you get an attack skill, then you can mix that in.
Also, if you do make a power, don't learn the first skill you buy from the Skill Master.
Its mp is double that of the level 20 TM skill (Burning Rave) and it's damage is a bit lower, I believe.
Of course, I think Buffalos need it, but I'm not to sure.