I've been a graduate student for a long time. Which means I've been poor for about as long. I have a reasonable bar, but I don't have the money or the square footage to have a truly extensive or impressive collection of booze. Maybe someday. IMHO, the true calling of the mixologist--much like that of the chef--is to improve ingredients by combining them. Many of my cocktail ideas aim to improve common or inexpensive ingredients by making them work together. I've got nothing against top shelf brandies, cognacs, or liqueurs. I love them. But I'm generally not going to experiment with them. I consider it a more interesting (and, I admit it, a more affordable) challenge to make no-name brandy or ouzo or Midori (seriously, I'm making a go of it) sing.
My favorite classic cocktail: the Manhattan. Nothing tells you more about a bartender than his recipe for a Manhattan. Always the first drink I order when I try a new place.