Definitely N'kulu (my bushmen oriented faction).
N'kulu warrior notices a plane
N'kulu pray to black-armored god.
N'kulu hunts down cart of white man
N'kulu captured slave
N'kulu celebrating after capture of castle.
One dude from N'kulu mastered shield&spear&no-armor fight to the level of beating everyones' asses in PW.
I've tried various themed factions, but probably nothing can beat N'kulu.
Also, making maps for PW gave me tons of fun (you can view them in my forum signature).