Take a tour and meet Key West celebrity flamingos, Rhett & Scarlett.
Feels like an obligatory stop, no?
Kermit's is a Key West institution. They have several locations however the shop on Elizabeth Street is the original location.
If you're driving down from Miami, make a stop at Robert's Fruit Stand in Homestead, Florida. They sell fresh fruits, smoothies, and have a small farm area with animals. Great place to stretch your legs and grab a snack.
Mallory Square offers shops, restaurants, and great sunset views.