Found footage? Hmmm... The Blair Witch Project is a bit of a classic, and subgenre defining, even if a similar premise in The Last Broadcast preceded it (everyone seems to forget that film). Then of course, the prank element is akin to the BBC's 1992 Ghostwatch, or even Orson Welles's notorious radio prank with War of the Worlds in 1938.

My favourite found footage film is probably the Norwegian film Troll Hunter. Hilarious, and highly recommended. :)