Lucanus elaphus a.k.a. the Giant Stag Beetle. No scale in the photos, but it was about 3 inches long.
As a kid, I always imagined these were so terrifying and rare, that if I saw one, it would be the last thing I ever saw before I was decapitated and ground into paste. Plus, they are constantly stealing your energon cubes.
But, hey, I'm still here!