Funny, favorite bars can be for so many reasons - some of mine are not because of any redeeming qualities, but just because I ended so many nights there. Regardless:
Angel Share, New York. A hidden cocktail obsessed spot before hidden cocktail obsessed spots were en vogue. Quiet and intimate, if there isn't a seat for you, you can't come in.
Brandy Library, New York. Clubby, with big leather lounge chairs. An exhaustive list of whiskeys. Similar to Angel Share, there's a no standing policy.
Blue & Gold Bar, New York. A true dive. Haven't been in a while, but 3 songs on the juke box were 50 cents and a game of pool 75. They were famous for not making drinks with more than two ingredients.
Bar at the Soho Grand, New York. Swank without being trendy and, like the rest of the Soho Grand, dogs are 100% welcome.
Charlie's Kitchen, Cambridge, MA. For no good reason. The food is pretty awful, but the beer is cold.
Clubhouse of the Myopia Hunt Club, Hamilton, MA. The real deal. As WASPy as it sounds. Members and guests of members only.
Constellation, Shanghai. Like Angel Share, but in China. Just about the only place here with a decent bourbon list. Luckily, it is a fantastic bourbon list.
Monkey Lounge, Shanghai. Walk down a foul smelling, trash strewn alley, open a non-descript door, and find relaxed lounge with Varnier Fanierre at a very reasonable 700 RMB a bottle. It may be filled with expats, but find me a bar in Shanghai that's not.