Ok, here is (IMHO) the ultimate 6-person party, dominant in combat, adventuring, and intrigue, all:
1 human fighter
1 half-orc fighter
1 human cleric of Pelor
1 human cleric of Heironeous or St. Cuthbert
1 human wizard (mage, evoker, or diviner)
1 halfling rogue
Forget the bards and rangers...