It's horror movie season in the US and my favorite type is zombies. I also love campy B movies. Watching Dead Snow 2 right now and I think it ranks up there with Shawn of the Dead and Evil Dead 3: Army of Darkness.
I like that it's such a simple concept for a horror movie, but it's still highly engaging for the audience.
spoiler
Early on in the movie, it (quite literally) teaches you a set of rules that the monster operates by, and the rest of the film feels almost like an interactive game.
the monster is a shapeshifter
it has stack (as in the data structure) of targets
it's always walking straight towards the target at the top of the stack (peek())
the target can have sex with someone else to make them the new target (push())
if the target at the top of the stack dies, the previous target is the target again (pop())
Beyond that, the writing and cinematography just let the audience play along. The characters are deliberating their plans on how they would deal with the monster, letting you also think about what you would do in their situation. And the camera likes to slowly pan around the people talking so that all the while, the audience is scanning the background looking for the monster. It can look like anyone, and they constantly, and deliberately put extras in the background walking directly toward the camera just to make you go "oh shit! Is that it right there? Hey, pay attention, we need to move!"
It's just such a fun, unique experience. I don't know of another horror movie experience quite like it.
I also loved It Follows. I was already hearing the soundtrack, before i saw the Movie. It made the movie feel so familiar, while at the same time experiencing something completely new.
The score composer, Disasterpeace, otherwise makes game music. This may have added to the game feeling.