The Suprise episode features the gift of a Claddagh ring between Buffy and Angel

Irish Claddagh rings were originally meant as a sign of love as an Irish wedding band.  Angel, who was supposedly born in Galway Ireland, does have a strong love for Buffy, but the matrimony part seems to escape him.  Irish Claddagh rings were founded in Galway Ireland, so no doubt, Angel knows the original intention of the ring.  And although the Claddagh ring is given now as a symbol of love and friendship, Angel proceeds to give the ring prior to consummation. (The Claddagh ring is not normally associated with consummation- get married first !) 

Angel's Claddagh ring was a powerful symbol of Buffy and Angel 's love

In the "Suprise" episode, Angel (David Boreanaz) gives Buffy (Sarah Michelle Gellar) a Claddagh ring, tells her he loves her, kisses her and yes, they consummates their relationship.  The Claddagh ring is used as a representation of Buffy and Angel 's love throughout the second and third season's.  The ring is shown in the opening of Buffy during season three.  Buffy later uses the ring, which possesses their love, to bring back Angel from another dimension.  The Irish Claddagh ring while symbolizing Buffy and Angel's love, also has become a symbol for those that love the show.  David Boreanaz himself wears the ring, which was said to be given to him by his girlfriend.