Source: The Deadly Mantis
Location: From Antartic Ice sheets to a neighborhood near you
Threat Assessment: 7. Not Godzilla level, but certainly a real threat. Super strong, tough, and capable of flight. Also, armed with very sharp, pointy claws.
Limitation: Insect intelligence.
Personal Note: I have seen real mantises catch humming birds. I have no idea why there hasn't been more done with these creepy crawlies.