Bourbon. Good bourbon. Not radiator fluid like Jim Beam. Definitely not rot gut like Jack Daniels (not a bourbon, anyway). Maker's Mark. Wellers is good (MM and Wellers are wheat bourbons, most are rye). For the cost conscious (me), Elijah Craig is a nice bourbon. Mix it with ice.
Guys don't ask a busy bartender to make them a mixed drink. You can lose your man card for that.