There are a number of things that make Reaper so easily identifiable, but you can most likely narrow it down to the original skin's mask and his twin shot guns. Making your own mask might be a somewhat daunting prospect, but if you're too late to purchase your own mask (painted or unpainted) from a variety of online sellers, you can take a look at some of the other mask designs Reaper sports throughout the game.
This particularly super-casual spray combines the original mask with a blank hockey mask -- a super easy find during this season's love affair with classic Jason horror.
And trust me, if you're planning on doing a Halloween costume of Reaper, nothing is too silly. Even the officially licensed version you can buy from Spirit Halloween falls pretty short of our dark, soulless edgelord. So if you want to spare your wallet and wear something just as good, check out the DIY instructions on the next slide.