Improvised Weapon: Scully left her gun lying on the floor in a next room, so when she fights with Incanto, she stabs him with nail scissors.
Horror Hunger: After the killer breaks his MO and kills a hooker instead of the usual lonely women looking for Mr. Right, and the crime lab finds traces of his skin that contain absolutely no oils or fatty acids, Mulder suggests that he kills women and steals all their body fat not out of some psychotic impulse but instead because of this trope. The killer later confirms this.
Kiss of Death: The killer uses kissing as a pretense to regurgitate acid into his victims, pre-digesting their flesh so he could suck out their fat.