I'm usually good at this game, but this one has me stumped.
The basics: zone 7, part sun and shade. This is growing in the "birdfeeder garden." It was a volunteer that took off.
Specifics: It grows like mint -- aggressive/borderline invasive, with similar root structure. Leaves are opposite and in pairs, like Noah's animals. Square stem. It is very hardy, tolerating foot traffic. Sure looks and grows like a mint, but here's the catch: it has no fragrance, including when brushed or crushed (as in rolled up in one's hands). No flower or bloom as of yet. I'm baffled.
As for the images, I included my garden sneaker some of the pics for scale (size 10 - men, if you were wondering).
So far, I, and a friend and long-time gardener and member here on Long Island, and buddy who happens to be a NY Master Gardener have yet to come up with the answer.
(this one shown growing with sweet woodruff and edging lobelia)