Rotarycraft a PvP mod? The same mod that has a gun that instant kills every player (apart from Reika since he decided he shouldn't die)? heh
Witchery is a really, really good PvP mod, though, lots of unique mechanics to keep it all fresh.
Bm can be cool, but is too overpowered in the confines of normal PvP
Botania has some cool stuff that can help with PvP, so that could be a interesting thing to look at (in 1.7)