What's your favorite?

Against all situations I take the same setup, normally ending up with a flawless victory on first try on normal diffculty.

2 Heavy Armored Soldiers (Maxium Equipment)
2 Sniper Hunters (Maxium Long Range Equipment and spare Equipment on Daggers)
2 Healers (Maxium Daggers)

Using 2 Barricades to create a chokepoint and a Latern just for fun...

2 Healers might be a bit redundant, yet they can heal each other or save a severly wounded Soldier

For me it's very often (i.e. not always : For a surprise attack, I will probably take a much more armored build) :

2-3 soldiers, heavily armored, to hold the choke points
1 experienced healer, to keep them in the fight
1 hunter, to stike at the medics and give the "coup de grâce" to the wounded
1-2 scouts, to make quick strikes from behind the soldiers and give flanking bonuses

Sometimes, 1 soldier or 1 scout will be replaced by my scholar.

I get flawless victories on normal most of the time, too, when I get defensive (barricades, natural choke points, lanterns...). The build is not so good when I want to take the offensive instead, though.

2 soldiers, 1 healer, 1 hunter, 1 scout. With the sixth person chosen as fits the circumstances. Either a third soldier for astraight on fight, a second hunter for a single choke point or a second scout when I want mobility. I used a scholar at first, but that didn't match my tactics enough.

Towards the end of th game, my lieutenant soldier would start the fight with one move action, then use the lieutenant special ability to have everyone else do a few "free" steps towards her. That would let my hunters and scouts get into better starting positions.

Pre-Native units:
-2 Soldiers: One's kitted for defense, one for offense and flanking. The offense one is always Mendoza for the polearm.
-1 Scout: MAXIMUM FLANKING. Works with my offensive soldier.
-2 Hunters: Level up ASAP for Quick Shot and then let sit for a while.
-1 Doctor: I find I don't need Revive that often, so I don't level 'im up as quickly as some do.

With Native Units:
-1 Soldier: The Soldier is still in general the best tank, although this'll probably be replaced by the Warrior when I recruit him.
-1 Champion: Aaawesome. Like a Soldier but more offense-oriented and... cooler.
-1 Amazon: Also awesome! High damage, uber high crit chance (and I forgot to take the perk that boosts it >.>), high movement, good ranged attacks, and cool abilities.
-1 Hunter: Yup
-1 Trapper: I like the Trapper more than the Hunter, as it takes the most useful Hunter skill (Quick Shot) and replaces the other two with more useful ones.
-1 Doctor: Ayup.

I had Mendoza with max promotion. Gave her the flanking bonus. She cut through enemies like butter.

After finishing the campaign I got the most succesfull battles with

1 Lt. Hunter with an arquebus
1 Sgt. Amazon with her uberpowered "deft strike"
1 Sgt. Medic who normally just provide smokebomb cover and patches up cursed and wounded units
1 Veteran Medic in case the other Medic gets poisoned or injured - OR - one one Shaman with a poison Attack, pretty strong for a healer but weak defense
2 Veteran Soldiers to soak up the damage

My Strategy normally involves stunning an unfortunate opponent then either flanking them to death or attacking him with point blank critical Amazon/Hunter Ranged combat.

3 Soldiers (all sword&shield, stun all day)
2 Scounts (dmg and flanking)
1 Medic (you oviosly need one medic)