Drambuie is a Scotch whiskey liqueur flavored with herbs and spices and sweetened with honey. While the history of Drambuie is unclear, a wonderful story has evolved telling that Bonnie Prince Charlie (a.k.a. Charles Stuart, the Young Pretender) drank a secret elixir during the Jacobite Uprising of 1745-46.
Upon his defeat at the Battle of Culloden, Bonnie Prince Charlie fled to the Isle of Skye. In gratitude for ferrying him across to the island, Charles gave the recipe for his elixir to the captain of the ship, John MacKinnon. Eventually, the recipe came into the hands of James Ross, who ran a hotel on the island. He commercialized this recipe, eventually exporting it to the United States. The name Drambuie comes from A Dram Buidheach -- The Drink that Satisfies. Ross eventually sold the brand to the MacKinnon family (no, not the earlier MacKinnon family), who make the liqueur today.
Drambuie now comes in three styles: the regular Drambuie, a 15 year version that uses Speyside whiskies, and a limited production called "The Royal Legacy of 1745". Drambuie has cloves and saffron in it, along with heather honey.
Drambuie is classically known in the cocktail world as being part of a Rusty Nail.