4% hit is softcap for spells in pvp, 6% hit is hardcap (negates racials).
Other than that, the spell-miss talents like rogue and ret (4%) cannot be negated with hit (not sure if that works right now, but thats how it was back in the day).
The other talents like improved blink of mages or the paladin talent sacred cleansing can make your spells miss (resist) too.