This is one of my new favorites. The Rusty Nail is the quintessential two-ingredient drink of the American recreation room.
Not much to say here, except drink it responsibly. It's a kicker of a drink and goes down smooth, so it's easy to over-consume.
3 oz quality Scotch (I currently have Glenlivet 15 Year French Oak Reserve in my cabinet, so that's what I'm using)
1 oz Drambuie
Shake together with ice, and pour into a double old-fashioned glass with ice. If it's too strong, you may want to either add a splash of water or wait for some of the ice to melt.
Some folks make it 2:1, some folks swear by 1:1. You could start out 1:1 and keep adding Scotch until it's just right for you. I'm partial to the 3:1 mix, since it Drambuie has a good bit of sweetness to it. Whatever you do, enjoy.