My Favorite:

The Claddagh ring is a traditional Irish ring given in friendship or worn as a wedding ring. The design and customs associated with it originated in the Irish fishing village of Claddagh, located just outside the old walls of the city of Galway. The ring was first produced in the 17th century during the reign of Queen Mary II, though elements of the design are much older.The Claddagh's distinctive design features two hands clasping a heart, and usually surmounted by a crown. The elements of this symbol are often said to correspond to the qualities of love (the heart), friendship (the hands), and loyalty (the crown). The expression which was associated with these symbols in the giving of the ring was: "With my hands I give you my heart, and crown it with my love."
The way that a Claddagh ring is worn on the hand is usually intended to convey the wearer's romantic availability, or lack thereof. Traditionally, if the ring is on the right hand with the design facing outward and away from the body, this indicates that the person wearing the ring is not in any serious relationship, and may in fact be single and looking for a relationship. When worn on the right hand but with the design facing inward toward the body, this indicates the person wearing the ring is in a relationship, or that "someone has captured their heart". A Claddagh worn on the left hand ring finger, facing outward away from the body, generally indicates that the wearer is engaged. When the ring is on the left hand ring finger and facing inward toward the body, it generally means that the person wearing the ring is married. Yet another legend of the ring states that if you are wearing the ring on the right hand and the band breaks, the person you are with is destined to be your true love.
The Irish Potato Famine (1845–1849) caused many to emigrate from Ireland, and the Claddagh ring spread along with the emigrants to the United States and elsewhere. Now the design is worn worldwide. These rings are often considered heirlooms, and passed on from mother to daughter as well as between friends and lovers.
A "Fenian" Claddagh, without the crown, was later designed in Dublin for the Irish Republican community, but that is not an indication that the crown in the original design was intended as a symbol of fidelity to the British crown. The Fenian Claddagh, while still being made, has not approached the popularity of the ancient design.

Claddaghs continue to be worn, primarily by those of Irish heritage, as both a cultural symbol and as engagement and wedding rings. At their Celtic Pagan handfasting, Scottish American musician Jim Morrison of The Doors and Irish American author Patricia Kennealy-Morrison exchanged claddagh rings. A picture of the rings was included on the cover of Kennealy-Morrison's memoir, Strange Days: My Life With and Without Jim Morrison, and the claddaghs can be seen in most of her author photos as well.
Claddagh rings have made periodic appearances in movies and television, often as a plot device to indicate the relationship status of a character, to illustrate wedding scenes, or to subtly indicate that the relationship of two characters has changed. In a scene loosely based on the above wedding ceremony, Val Kilmer and Kathleen Quinlan, as fictional versions of Morrison and Kennealy-Morrison, are seen exchanging the rings in Oliver Stone's movie, The Doors It was also used in the Kenneth Branagh film "Dead Again" as a plot device in one of the early scenes.
Sometimes authors of fiction and fantasy works have given the ring a somewhat altered or fanciful symbolism to better suit their purposes, such as writer/director Joss Whedon's use of the ring as a recurring plot device in the television series, Buffy The Vampire Slayer. Whedon reinterpreted the meaning of the ring - when worn on the left hand, facing in, in the usual "married" configuration - as meaning, "the wearer is destined to be with his or her love forever." While the actual meaning ascribed to the ring in this instance is incorrect,[ it is used in much the same way as claddaghs have been used in more traditional roles in fiction: to provide an ongoing visual reference to the type of relationship that exists between two of the lead characters, Buffy and Angel.- From Wiki