Any items you never use during the gameplay? Personally, I never use any of the X-items that boost stats during battle. It just seems much to skip a turn just to do that.
I dont use the orbs that give status problems to the holder (Toxic Orb, Flame Orb) and I don't use any of the Insences (Lax Insence, Gold Insence) I prefer selling them. Neither I use any TMs that teach status moves like Safeguard and Light Screen.