Here's the rough guide to
Gestalt: a PC should be able to get all good saves, get at least d8 HP, and get two sets of abilities: one active / offensive (like spells), and one passive / defensive (like Divine Grace or Evasion). You should also be able to get a load of skill points.
Here are some more optimal combos:
Wizard // Ranger (archery path) -- Skill points, hit points, all good saves, Evasion at 9th level, full BAB, and something to do when your spells run out or when you run across a magic-immune foe. Favored Enemy bonus damage works on weapon-like spells, and full BAB + free Improved Precise Shot means you do
not miss with your Ray spells.
Psion // Warblade (from Tome of Battle) -- The ultimate brains-over-brawn melee machine. Your bonus Psionic feats make you hit faster and harder than a Warblade otherwise could, and that's pretty darn hard already. Also, you're a full manifester. Int bonus goes to damage, "spell" DCs, Reflex save, and a pile of other things -- you're tactically flexible, but you only depend on Dex, Con and Int.
Wilder // Paladin -- Yes, Wilders can be Lawful Good! What's the big deal here? Charisma to saves and Touch AC, Charisma to "spell" DCs, and you can "cast" in fullplate. This is your armored artillery platform.
Druid // Rogue -- Pounce + Sneak Attack = win. All good saves, Evasion, great skill points. Sure, take one level of Monk if you really want Wisdom to AC before you can afford a Monks Belt, but no more. Unarmed strike does nothing for you, and Rogue // Druid already gives all good saves.
Cleric // ... anything -- Clerics own, but you need to pick what kind of cleric you want to be. Evil clerics aren't as easy to play, since they suck at healing.
Fighter // Cleric would be nice for someone who wants to play a feat-intensive Fighter build; the strength of the Cleric side will compensate for the weakness of the Fighter side.
Bard // Barbarian -- All good saves, great selection of class skills (though not all that many skill points since Int is a dump stat), Inspire Courage song works fine with Rage (but many other songs don't); good mix of active and passive abilities. Archery is a surprisingly good choice, since Inspire Courage damage compounds quickly when you get a lot of attacks. Unlike other archers, though, you're not a squishy little dude afraid of melee.
Barbarian // Dragon Shaman -- Rage increases your breath weapon DC by at least +2.

With your BAB, HP, weapon selection and aura, you fit well in the center of melee.
Bard // Warblade -- Pump Dex, Int and Cha; have a decent Con and Str; don't worry about Wisdom. Focus on Diamond Mind and White Raven schools. Buy a Ring of Evasion and you are a dervish of dancing death. Again, all good saves.
Beguiler // Warblade -- Int synergy.
Swordsage // Cloistered Cleric -- Very strong, excellent Wisdom synergy, good mix of daily and per-encounter powers.
Cheers, -- N