1) Swêboz

Their units all have decent (above average) morale and lethality, as well as better discipline than other barbarians.
Their unit skins are probably my favourite ones in the whole game. And of course, I like the units as such, as well as their culture and language in general. The only serious drawback (apart from the lack of armour, which is a general Barbarian issue) is their pathetic economy, which is the third weakest (after Sauromatae and Saka) in the game.


2) Casse

Love those woad paintings. They got some of the best warriors in the game (and some of the weakest), and their position and some other factors make them very interesting for me.


3) all others; can't really decide on one. Colour wise, I prefer the Arverni to the Aedui, but I like the Carnutes better than Arjos. A major factor in favour of the Gallic factions is their economy, IMO. Lusotannan have some great units, as do Getai. Getai are awesome too due to the fact that their units have the highest morale on average, and their roster is one of the most diverse in the game.