Pernod is an anise-flavored liqueur from France, which lends a licorice-y flavor to whatever it's added to. It has a particular afffinity with seafood dishes. Classically used in bouillabaisse and oysters Rockefeller, it's also delicious added to mussel-cooking liquid and cream sauces for fish.
Of course, you can also drink it, as the French do: Fill a tall glass with ice and add one part Pernod to four parts water.
Other anise-flavored liqueurs, such as absinthe or Pastis, can lend a similar flavor to dishes, though the products are not identical; go slowly when substituting and adjust the amount to taste.