The Voice finale

RAISING THE VOICE: Rihanna, Kelly Clarkson, Bruno Mars and The Killers will perform on the Dec. 18 season finale of The Voice, NBC has shared, as will a special guest to be named later. Rihanna will perform "Diamonds," Mars will play "When I Was Your Man." The Killers will offer "Runaways" and Clarkson--who burst into the spotlight on arch-rival reality-competition series American Idol but has since been a Voice guest mentor and appeared on Duets--will bust out "Catch My Breath." And clear your DVRs for the latest music-reality-competition series, American Trade Weasel, which will feature a trio of paunchy dudes competing to the predict first-week sales numbers on assorted releases and stuffing cold cuts into their gobs. (12/13p)