Complete Psionic introduced a few new classes, chief among them is the Ardent which could basically be described as the Psionic Cleric.
The Ardent is a class that draws upon philosophical concepts, which serve as the inspiration and theme for their psionic powers. You could go into as much or as little actual game mechanic detail, but I'm curious just what sort of ideas would someone have for a planar Ardent.
I'm sure factions and sects have a bunch, with some mantles related to their faction, and a few coloured by their own personal experiences and views. Of course not all Ardents would be connected to organizations, some might actually be independant philosophers...
Then there's the Divine Mind, which is like the Psionic Paladin (or Marshall from the Miniatures Handbook). Complete Psionic tries to tie them closely to gods, but I'm more for having them as seperated from gods as Ardents are, and just being like a more militant version of an Ardent.