Slayaway Camp: Butcher's Cut

You can unlock killers from the Mystery Box in the main menu with coins, but it is much easier to use Killer Kodes. Press and go down to “Killer Kode” and enter any 13 of the following to unlock killers:

adieutube
badu
beaster
campgate2016
comewithme
forhades
Freshmaker
gnollnumbertwo
griffin
gygax
lichee
nananananananana
slashback
smiggles
theyfloat
wristrocket

You still need to buy one with coins for "Needful Things".