The Burrowers (2009). Starring Ethan from Lost, Kurgan from Highlander and Eugene Victor Tooms. Also some cool-looking monsters!
Look, I fully realize that not every movie has to have a happy-happy ending... especially when it comes to horror movies! But this one was just lazy. I mean, you know you've got a problem when I, myself – scarcely a Hollywood movie writer, at that! – can think up a better downer ending than the so-called professionals... and one that wouldn't waste the aforementioned cool-looking monsters, to boot!