Bourbon, on the rocks (good bourbon, like Woodford Reserve, Pappy Van Winkle, etc). I'm from Kentucky, it's in my blood.
Vodka and club soda - either with a couple slices of lime or use infused vodkas. Very light, summery type beverage.
Occasional good tequila - Herradura, Patron, etc. El Jimador with juice from half a lime and a club soda on the rocks is delicious.
Very occasional beer. More than a couple makes my stomach hate me.
Key to my liquor consumption is the lack of mixers other than a rare mojito when I go to our killer Cuban place. The only calories are from the alcohol, which is 7 cal per g, if you care about calories...~25g per oz of alcohol, so an 80-proof liquor is .6 g of alcohol per 1.5 oz shot, or 105 calories per shot.
Yes, I know a lot about alcohol...it's part of my job. ;-)