As Seen In: Scanners (1980)
The master of bodily harm and perverse mutations, Canadian auteur David Cronenberg has blessed gore fanatics with all kinds of nastiness, from the titular beast in The Fly to James Woods and his vagina chest in Videodrome. When pinning down the filmmaker's grossest handmade effects, however, there's really no contest—Scanners takes the prize.
Scanners, written by Cronenberg, presents a world in which people with strong telepathic abilities can kill, simply by using their minds. One "scanner" in particular, played by Michael Ironside, has gone rogue, and he decides to show his rebellious power by making a speaker's head explode during a press conference.
First, the poor guy begins nervously shaking, glancing over at a deep-in-thought Ironside; and then, boom! His head detonates as if someone hid a stick of dynamite in his brain. Try dealing with a migraine without panicking after watching Scanners.