While you could get your groom cufflinks, a tie, or a money clip, my favorite groom gift is cologne. It can be one of his timeless favorites, a new one that when he wears it, it will remind you both of your wedding day, it can be a vintage one that you found in a cute boutique, or one that goes with your wedding.
Plus, it's the gift that gives back to you: a great smelling husband to be.
