If there's one horror sub-genre that's never been fully appreciated, it's found footage.
That's partly Paranormal Activity's fault, as after that flick rocketed to huge success in 2007, everyone wanted in on the action.
It would be wrong to write off the whole sub-genre though. When done right, these movies can be hugely effective, mining scares from the intimate POV the audience is confined to, and allowing for more personal takes on horror stories that have otherwise been done to death.
For as pigeonholed as found-footage gets as well, a good filmmaker knows how to bend the rules of the structure and defy expectations to deliver genuinely innovative experiences all horror fans need to see.
Now, just to clarify a few things before we jump in. First, there'll be no 'screen movies' like Host or Unfriended here because, while you definitely should watch them before you die, they both reflect a new horror sub-genre in its own right.
Likewise, Cannibal Holocaust and The Blair Witch Project are the two biggest influences on the entire genre and have been talked to death, so they make it on the list here as honourable mentions.