As fun parties I like themed partys the most:Currently I have a ranged-weapon-party (2x Human Ranger, Dracon Ranger, Gnome Gadgeteer, Felpurr Ninja, Elven Bishop and Vi with Blunderbuss), the martial arts - team (Elven Monk, Human Monk + Felpurr Ninja & RFS81) and a pure caster-group (Gnome Alchemist, Dwarven Priest, Faerie Mage, Mook Psionic, Human Bishop and Elven Bishop, they are also dragging Urq along at the moment).
I simply love the rangers taking down a group of critters down, before these are able to get into melee range.
As a martial arts team it's fun being surrounded by a group of six fighters, with half of them just defending each round, because the Monks and Ninja are too stealthy to be aimed at. In turn, we take the fighters down one by one, often with critical hits.
And it's spirit lifting to see the group of 10 Rapax shrink, after the sixth Iceball / Noxious Fumes / Psionic Blast / Tsunami / whatever is cast on them in one round.