Rusty Nail

The cocktail, Rusty Nail, is a combination of Drambuie and Scotch whiskey.

The ratio of 2 ounces Whisky to 1/2 ounce Drambuie seems to be popular but you are encouraged to try your own according to taste.
Lots of ice in an Old Fashioned glass, and stir.

Variations include

The Rusty Bob, which substitutes Bourbon whisky for blended Scotch whisky
The Rusty Ale, in which a shot of Drambuie is added to any beer, served without ice.
The Smoky Nail, which uses Islay whisky (very smoky in flavour) in place of blended Scotch whisky.
The Clavo Ahumado (Spanish for "smoky nail"), using mezcal instead of blended Scotch whisky.
The Railroad Spike, often served at brunch and made with approximately four parts cold brewed coffee to one part Drambuie in a tall glass over ice.

The Donald Sutherland, which substitutes Canadian rye whisky for blended Scotch whisky.