Signature Cocktail

What signature cocktail should serve the bride?
I am a bridesmaid at the wedding of my friend, and she asked me to help him choose a cocktail to offer its guests. She is having beer, wine and vodka, and can choose a more "signature" cocktail to serve the addition. Was thinking of a cosmo or Bellini, but I'd love to hear the thoughts of another person out there and I'm not a big cocktail drinker myself. Thank you!
Why is the bride services on their own wedding? There was a bartender and go have some fun. Manhattans are always classics.
Make the Steven Colbert Cocktail!