I play the Warden Wolves, Hell's Horses, Goliath Scorpions, FedCom/Suns, League- Regulans or perhaps Rim, and mercs . . . mercs in the Chaos March is my primary campaign at the time.
Do not play much past the start of the Jihad (have not advanced that far), but I like beating on Blakists, Falcons and Cappies. Hellions are a close runner up . . .