Anything with spells, armor, and decent attack.
So clerics and druids tank better than knights, fighters, and other classes of those sorts?
Yes. By an order of magnitude. Clerics get DMM. Druids get Cryohydra form. That's just off the top of my head. Also, spells > melee.
What about P.warriors, Hexblades, Duskblades, and other caster/fighter types...or is that the definition of Gish?...
Gish = fighter/mage combo in some flavor. I believe the default target is 8th level spells and +16 BAB, but that target moves a bit with various factors: some want 9th level spells at the expense of that last attack, some can manage to squeeze in both, some want no classes with less than d6 HD, some sacrifice 8th level spells for other abilities, etc.
All the classes you list are gish to a certain extent, though Hexblade is probably the weakest of those options. Key factor is still access to spells or spell-like abilities. They all do better in late game (after level 14) than straight melee types, assuming a competent player and DM, and they all appear to lag slightly behind straight casters or straight melee types in early game, while they're setting up, barring extraordinary circumstances.
What 8th level spells are the target? That one that makes you colossal?
Divine metamagic... That's that trade turn attempts for extra spell levels of meta magic like 4 turns for a maximize feat isn't it... Okay I remember that.
What 8th level spells are the target? That one that makes you colossal?
Because losing caster levels = BAD. 8th is a reasonable compromise without losing an iterative attack - though you can get extra attacks through magic. As indicated, some gish builds strive to hit 9th level spells.
It's not even difficult to figure out now that Abjurant Champion is around.
Fighter 1/Wizard 6/Spellsword 1/Abjurant Champion 5/Eldritch Knight 7
-17 BAB, 9th level spells, CL 18
or
Human Paragon 1/Fighter 1/Wizard 2/Human Paragon +2/Spellsword 1/Abjurant Champion 5/ Eldritch Knight 8
-18 BAB, 9th level spells, CL 17
both are pretty standard gish builds, though you can get very exotic. A lot of people like to go specialist Transmuter for the wizard levels to get more buff spells per day.
Your AC is through the roof, your offensive output is through the roof, your versatility is amazing, and you can pretty much do what you want. The mid levels are a lil bit more work, as was mentioned above.
Psi Warriors and Duskblades are essentially "Gish in a can". They can both tank fairly well, though in the end run, a gish is probably better. Psi Warriors get very beastly though if you use em right and take the right PrC.
Hexblades don't make great tanks usually.
At this point the standard gish is +17 BAB and 9th level spells.
It's not even difficult to figure out now that Abjurant Champion is around.
Fighter 1/Wizard 6/Spellsword 1/Abjurant Champion 5/Eldritch Knight 7
-17 BAB, 9th level spells, CL 18
or
Human Paragon 1/Fighter 1/Wizard 2/Human Paragon +2/Spellsword 1/Abjurant Champion 5/ Eldritch Knight 8
-18 BAB, 9th level spells, CL 17
Yeah, I forgot to revise my numbers with Abjurant Champion in mind; the threads I typically referenced for gishes predate CM.
CoDs dont need tanks, and deal with tanking by getting reach and beating on people.
True, but if they WANT to tank or you're looking for the BEST tank. It's probably, in order:
Druids
Clerics
Archivists
Wizards
Other Full casters
Non-casters