"Day 20 - Your favorite horror film involving a killer animal"
There's only one right answer to this: Fuckin' "Day of the Animals"!
I have 7 words for you: "Leslie Neilsen Wrestles A Fucking Bear SHIRTLESS!"
I mean, do I need to say more? Well, ok I guess I'll give a small plot description.
Something with the Ozone Layer has caused animals all over the world to freak out and start attacking non-animals (AKA humans). Kind of a sucky time for a group of people to go hiking in the woods. Soon, they're attacked by every animal you can think of, including bears, which Leslie Neilsen, who at this point proves he cold play douchebags before he became a comedy legend, gets shirtless and wrestles a bear. There's not any real reason for it besides MAKING AN EPIC MOVIE!
The rest of the movie is your standard faire but stick around for the wrestling bear scene. Oh and to see Leslie Neilsen try to rape someone. Your mind will be blown!