I like how the Culligan Man always declares his entrance when entering a home. In all of the commercials, he never knocks, he just opens the front door, walks in, and announces, "Culligan Man!"
I think it would be fun if everyone adapted this process. I would walk into a restaurant and shout, "Hungry Mexican!" or enter a department store and declare, "Guy looking for a jacket!" or go into Staples and say, "Cheapskate looking for small items that will fit in my pocket!" or go to the movies and yell, "I have snacks hidden under my shirt!"
That way everyone knows who everyone else is and we can go on from there.