Two classes that are almost tied:
Wizard - I like playing thinkers, and a wizard typically has the Int to back that up. I also like planning out what I think I will need, spellwise, for the day.
Paladin - so many ways I can have fun as a goody two shoes religico.... The Knight in Rusty Armor, the Snark Knight, Captain Marvelous, and White Hat Cowboy. Right now I am playing a paladin, started off based on Gene Autrie, but has been leaning more toward Paladin (from Have Gun Will Travel). There is an odd friendship going on between him and the Summoner's Eidolon.... A few times he has woken up with the Eidolon snuggled up next to him.
The Rogue or Bard is also fun, I like playing a face rather than a thief - a con man, a raconteur, or just plain a meddler.
The Auld Grump