I'd say BHG and criminals are my favorite... me and Grimly were forced to peace as we sat around FP1, a Zoner Destroyer sitting there... the ensuing RP was fun, as was the chase when Grimly broke for Cadiz (he got away with 50 bots left on his Praet), but it became apparent that the BHG fought the Corsairs for money, and the Corsairs fought the BHG for sport/survival.
I also like interactions between my LN and the Phantoms. Always fun.