Readerbreeder said:
It does indeed look like the monk is a good choice for the well-rounded gestalt character. Has anyone else found any unexpectedly powerful or synergistic class combinations?
Core:
Monk/Druid (WIS to AC, fast movement in wildshape, natural armor bonuses)
Bard/Sorceror (Buff/utility from the Bard, blast from the Sorceror, single stat casting)
Paladin/Sorceror (Never fail a saving throw, True Strike/Power Attack/Divine Might/Arcane Strike Smite)
Fighter/Cleric (Remember all those warrior Cleric builds?)
Rogue/Wizard (load up on ray spells and spells like Invisibility and Hold Person-- take advantage of ranged touch sneak attack)
Some of these require specific builds, but they're ugly enough to be worth mentioning.
Psionics and
Complete:
Rogue/Warlock (see Rogue/Wizard, above, plus all day functioning)
Fighter/Warmage (spend one feat at 9th level, cast spells in plate mail; replace Fighter with Paladin to get awesome saving throws).
Psychic Warrior/Scout (Archer build, Hustle + Rapid Shot)
Paladin/Monk 2 (or 4), Favored Soul/Sorceror X (never fail a saving throw
plus evasion, single stat casting for two full casters. Go with Pal/Mnk 4 to take advantage of Divine Might, but your caster level will suffer).
Psychic Warrior/Psion into Metamind/Psion (add your +1 manifester levels to Psychic Warrior, who won't miss losing five levels of powers. Manifest Schism before using Font of Power, Hustle every round, for three fully augmented powers/round for free for ten rounds; also, tons of psionic feats).
Fighter/Psychic Warrior (depending on DM interpretation, could be almost double Fighter bonus feats.)
That's all I can think of off the top of my head.