Hagfish, despite being named by a scientist who was clearly not a fan, are some pretty interesting fish.
Also known as slime eels (seriously, do you have to dunk on them this hard, biologists), they slither around the ocean floor, searching for food using sensory tentacles that surround their mouths. Once they find prey, they can enter the victim through their mouths, before eviscerating them from the inside. They can also perform this same feat by entering their prey through the gills or anus.
Mainly consuming smaller, live and injured prey, they have been known to scavenge on larger carcasses including sharks and whales.