That said, no, you can't hide the full-length shotgun under a trenchcoat. Nor the Katana. I don't care how many times they've done it in Highlander.
I go with the "Blade" motif. The handle is sticking out of the top. Still badass, but still credible.
I've allowed the Highlander "sword-in-ridiculously short coat" power as a cheap adept power. Of course, that same char got the "tingle" when other adepts were around. Used it to drive him fairly insane.