My wife and I always answer the door open carrying firearms. Of course, we always study the situation through the window/peephole first. We also have a huge promotional cardboard cutout of a Glock 17 hanging in window by the front door.
We don't get too many visitors for some reason... and we live in a really busy, tight, neighborhood, lol. The ones who do brave the trip up the steep hill to knock on our door usually comment about the Glock in the window. The comments are usually about how they expected us to be carrying.
Some may think the Glock in the window "lets criminals know" that there are guns to steal in the house. I think it tells criminals not to even try. Plus, we're responsible gun owners, the guns we don't wear are locked up good if we're not around.