Belt buckle = shiv

Found in a thrift store.  The best comment from the Reddit thread:  "Rick donated this after realizing that any combat advantages gained by having a small knife were immediately lost by no longer having his pants stay up."

And regarding shivs:

A shiv (possibly from the Romani word chivomengro, "knife") is a slang term for any sharp or pointed implement used as a knife-like weapon. The Oxford English Dictionary suggests shive, a razor, documented in 1915, as the root word.

Composite image made from photos posted at imgur.