If I had to stick to just one drink, it would be rum and coke zero. The better the rum, the less coke I add. Flor De Cana is my favorite.
But since I don't have to stick to just one, I also enjoy the occasional:
white russian
7 and 7
long island
scotch with ice
For beer, I like trying local microbrews, but if buying national brands, I usally get Blue Moon, Bass, Stella, Fat Tire, or Widmer or Pyramid Hefeweizen.