Top Five? No such thing.
![Very Happy :D](./images/smilies/icon_e_biggrin.gif)
I do try to match up a couple pets for each character - those pets then "belong" to that character and run with them always. Some of my favorite duos are:
Guardian Cub for my Protection Worgen Warrior
The Sunflower for my Undead Shadow Priest.
Onyxia Whelpling with my Human Affliction Lock
Baby Polar Bear with my Gnome Frost Mage
Hippogryph Hatchling for my BE Arms Warrior
Someday I want a baby Gryphon for my dwarf ret pally.