Most powerful non-magical class combo

[mr_outsidevoice]

Scout/Monk for Hit and Run Goodness. Stunning Fist and Skirmish means an opponent is worn down quick and not as able to retaliate.

Fighter/Monk for raw Martial arts power.

Fighter/Soul Knife

Knight/Marshall would be fun for a High Charisma Build character that isn't a con man or spell chucker. Good front line Leader.

Fighter/Rogue. Good especially for two-weapon fighting, several Sneak attacks when flanking.