I'll be the one to say it:
A glass of liquor of any sort, straight up or on the rocks, is NOT a cocktail.
A cocktail, by definition, must be liquor mixed with something else.
I don't know that I have a favorite, but if I did, it would probably begin with M, since I like Margaritas, Manhattens and Martinis.
By the way, Martinis are made with gin. If one asks for a Martini, there is no need to ask vodka or gin.