This is based on opinion. Please don't list it on a work's trope example list.
Nightmare Fuel / Hollow Man
The entire premise of the film, which has loads of Paranoia Fuel and Fridge Horror aspects to it. An already-unstable scientist uses a serum to become invisible and as a result loses his sanity completely to the point of becoming anAx-Crazy sociopath. There's also the fact that throughout the events of the film, no cure/ability to reverse the effects of the serum is able to be created/found, despite the attempts of his fellow scientists who he eventually turns against. And that's not even going into the implications of what one would do while invisible or what would happen to one who was unwillingly stuck with such a person without their knowledge. Special mention goes to one scene in which the Villain Protagonist, fully invisible, spies on his female neighbor and rapes her.
Here's some further Fridge Horror: unless invisibility somehow affects your sperm count, there's a very good chance that the neighbor was knocked up by a crazy invisible man. Who knows what the serum would do the baby...