At least on A2 my favorite combos consist of
~Viera: redmage (doublecast) summoner for a support class that can pack a punch
~Hume: dualwielding paladin with seer for magic frenzy, doublehitting on mobs is amazing (not to mention range attacks on a tank!)
~Gria: Hunter with tank ability mixed with ravager or raptor (geos fun but not to fantastic) Hell Gria is an amazing race to begin with but hunter on a gria with sneak attack? Phew that's broken on a flier
Also one of my favorites
~Hume: Dualwield illusionist mixed with seer for magic frenzy. Hits everyone with the typical illusionist attack BUT since I use magic frenzy I proceed to attack everyone twice with my staves. I also typically run a cannoneer alongside a time mage or two for mp shell and quickens.
I typically run parties of 3-5 people so I stick with my favorites. I go for variety in postgame

For pure funzies:
~doubleshield master monk baanga: I love this class just because it's such a fun one to play as with broken avoid. (the damage is quite fair too)
~Lightning rod anything: Used as a support for my mages to hit things out-of-range and a distraction to keep my squishy characters safe.
Also assassin/sniper combo is quite nice but I typically stick with vieras as my mages/support classes

~I may have forgotten some due to the fact that I haven't played this game in ages... after a while breaking the game and smacking it's mentally-disabled ai in the face gets a tad old. Also I realize that this is for advance but hey... A2 is similar