Creative Ring

Promise ring - A ring worn to remind a person of a promise.
Purity ring - A symbol of virginity in some religious cultures.
Puzzle ring - Interlocking rings forming a single band. A famous example is the classic Cartier "triple" wedding ring.
Poison ring - A ring consisting of a bezel with a secret compartment or made in the form of a container, used for keeping medication or poison (anachronistic use).