Creative Ring

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).
Regards ring - A Victorian engagement ring with an implicit acrostic: Ruby, Emerald, Garnet, Amethyst, Ruby, Diamond, Sapphire.
Rosary ring - Ring worn around the finger with 10 indentations (or protrusions) and a cross, representing one decade of a rosary. The rings are used to keep track of place in the prayer by rotating the ring on a finger and feeling the marks.