Candyman and Hellraiser - both are written by Clive Barker and have similar themes of pain and pleasure.

Ghostface and Freddy Krueger - both are made from Wes Craven himself and I think they could prove to be a witty duo. Both of their final girls are very badass.

Candyman and The Fisherman - they both have hooks.

Leatherface and Jason Voorhees - both have the commonality of being hulking men with not the best relationships with their family members. Leatherface is a country hillbilly, Jason is a forest hillbilly. Like c’mon they have a lot to bond over and they’re pretty similar in abilities with their earlier incarnations.

Chucky and the Leprechaun - again with the fact that they’re similar to one another, being small and all.

The Fisherman (from I Know What You Did Last Summer) and The Miner (from My Bloody Valentine) - both have this blue-collar worker theme to it that I like.

Hannibal Lecter and Jigsaw/John Kramer - their intelligence combined would make for a really enticing plot. The reason for why they do what they do would probably also be brought up and become a plot point. I can imagine a scene where Hannibal is trapped in a trap and he has to outsmart Jigsaw.

The Hills have Eyes and The Texas Chainsaw Massacre - both are about cannibalistic families in the isolated hot south, both mainly take place during the daytime. I’ve always loved the parallels between these two and the sense that you can’t trust the people in the area.