Video Game Secrets

[Chutzpar]

All are good points.
Leviathan is referred to anything unusually huge and ominous, though

Um, not sure what your point is :C
Leviathan in its everyday use - that is, to mean the biggest of a group / something abnormally big comes from the name of one of the princes of Hell. :E

But yeah 666 is overdone like whoa :C

Not much of a secret, but:
There's a gravedigger in V:tM - Bloodlines called Romero, who's defending the town from zombies.
And, y'know
George A. Romero.
Yup.

BEST SEKRIT EVAR.