[@Spinosaurus]
I'm currently going through my list of monsters and such looking for good ones. Also what time period? 

Some ideas:
Mothman (could go a few ways. One theory says it was some sort of crazy technology since it didn't fly so much as float. Or the fact that it was believe to be trying to warn the town about an upcoming bridge collapse. ))

[url=https://en.m.wikipedia.org/wiki/Flatwoods_monster]The Flatwoods Monster[/url] One of the creepiest alien stories I've ever heard. 

[url=https://en.m.wikipedia.org/wiki/Beast_of_Bray_Road]The Beast of Bray Road[/url] 
Possible werewolf or giant creature of the same kind. 

Bigfoot
I like what the SCP wiki(great for monsters) did with them. Look up SCP 2000. Basically the Bigfoot used to be the dominant species then humans turned them into monsters.