Hardcore, desperate alcoholics will do whatever it takes to get alcohol in their bloodstream, even if that means drinking mouthwash. Perhaps some of them even acquire a taste for its minty flavor, and Dr. McGillicuddy's was created with this niche in mind. I cannot easily think of any other reason for the existence of a liquor that tastes exactly like mouthwash, so there you have it.
I was first introduced to Ouzo a number of years ago by an old friend, who told me a story of how his Greek boss had insisted he drink it as some sort of perverse initiation into both manhood and gainful employment. He described the effects of this rite of passage as being “like getting kicked in the face by a donkey,” and urged me to always treat Ouzo with the utmost respect. Then, of course, he poured us each a few shots of it to illustrate his point.
If you like the taste of black licorice, you might enjoy Sambuca, an Italian liquor with anise flavoring. Sambuca is a drink for a couple of old Italian cronies to sip slowly at an outdoor cafe on a long, sunny day. The traditional way to drink it is with a coffee bean floating in it. This doesn't really do anything to the flavor on its own, but if you drink the Sambuca and eat the coffee bean, it's an interesting combination.