4. Ray Park - Reptile
Granted, the roles of Smoke, Reptile, Sub-Zero and Scorpion could be played by a lot of actors, and their "look" as such isn't particularly important given that we don't see much of the actors' faces. However, Ray Park has proven himself in a wide variety of slimy, lithe roles, most notably as Toad in the first X-Men film, and recently was one of the few bright spots in G.I. Joe: The Rise of Cobra as Snake Eyes. His creepy erratic movements and eerie, almost reptilian look would make him a perfect fit as the character. It's important to try and make the character iconic, too, because Sub-Zero and Scorpion are, of course, extremely well-known already, but Reptile, aside from a brief appearance in Anderson's Mortal Kombat film, is not known to audiences at large. It is crucial that Tancharoen gives Reptile an epic "moment" of sorts, perhaps getting one over on one of the protagonists, so he can become cemented in our mind as a series fixture for later films (assuming he isn't killed off here).