I'm a big fan of Samuel Smith's of Yorkshire, especially the Oatmeal Stout and the Imperial Stout.
Okay, and the Nut Brown and the Taddy Porter ...
pretty much any dark will do me, just so long as there isn't much in the way of sweetness involved. MMMMmm rich creamy dark beers ...
I liked the Blackout Stout down out Capitol City Brewing in Baltimore's Inner Harbor, but they don't have that all the time. Sometimes I have to settle for the Prohibition Porter, which is still tasty, but doesn't have the roasted chocolate goodness of the Blackout.