Pfft.....hmmm....
Long answer:
[spoiler]"Fighter" aswell as ToB:
Warblade, with Crusader at second.
Divine Caster:
Druids. With Clerics a long way down on second. I know I'm gonna sound wierd, but I don't like clerics.
Arcane Caster:
Sorcerer. Though I have far more Wizard -second place- builds, I prefer the sorcerer since I'm bad at preparing spells.
Manifester:
Psion (egoist/shaper). With Psychic Warrior at second.
ToM:
Binders. With Shadowcasters waaaaay down the line. There are no such thing as a Truenamer.
Incarnum:
Totemist, Incarnate at a respectable second place.
Skillmonkey:
Artificer.
Beguiler on second since:
I can't find a fighting style that I like for the Factotum. (I don't like the Ijatsu-route at all).
Swift Hunter isn't a single class.
Rogue ends up having only a single level, the rest being wizard, unseen seer and arcane trickster.
"Face":
Bard I suppose, since the Binder/Warlock/Hellfire Warlock isn't a single class
PrC:
Swiftblade, nothing even gets close to it, with one exception.
A concept that I love but won't work properly in 3.5 without gestalt:
Storm Sentry. The whole controlling the winds is a major love of mine.
But it either needs to be ported to 4ed or included into Gestalt to be worth it.
I also love the concept of a Gnome (Copper)Dragon Shaman. I'm soo going to do a party-enhancer if I ever get the opportunity in gestalt. Dragon Shaman and WoC-bard, perhaps some Song of the White Raven shenanigans. Might even add some Marshall, aswell possibly with some kind of mount-thing going on... suddenly those 40 levels seems too few
[/spoiler]
If I had to choose one character and only one to play for years to come, it would either be a sorcerer or a druid, since I need options. Nothing says options like casting.
I've always liked druids, every game I've played or seen that had them.
D&D, Heroes V, HORDES, Magic:the Gathering etc.
Of all the aspects of D&D, gaming wise nothing beats playing arcane casters for me. Since I prefer Sorcerers over Wizards 'cause I like spontaneous casting more, sorcerer gets my vote there.
Since I'm more comfortable playing high WIS than high CHA, Druid gets that.
Short answer:
I don't know.