Dear (Friends / Infidels):
As I sit here with an Afghan on my (lap / TV), I sip a bit of (yummy egg nog / weapons-grade tequila), and find myself reflecting on this (festive / festering) holiday season."
Frank Cerabino, "Trouble writing holiday letter?", Cox News Service, December 18, 2001
Joe Adcock, "'This End Up' is Amusing, Exhilarating Exercise in Exhaustion," Seattle Post-Intelligencer, November 13, 1990
So it's entirely natural that people have taken up the weapons-grade adjective and applied it to more mundane objects. Besides the tequila reference in the above citation, I've also seen weapons-grade used to modify the following things: drugs, salsa, peanut butter, cheddar cheese, punctuation(!?), and, uh, certain intestinal gases, referred to in semi-polite society as "wind."
Using weapons-grade in non-military contexts may be popular, bit it's certainly not new. I was able to trace this usage back over 10 years (see the earliest ciation).
Here's an even older citation, although this one uses a different "pro-gun" sense:
weapon of mass distraction