Ziya Tong and Dan Riskin learn about the latest cool gadgets just in time for the holidays during High Tech Toy Week. They'll review such inventions as a unique all-terrain vehicle known as the Ziesel, a bomb suit and a civilian aircraft. Discovery, 6 p.m.
How I Met Your Mother
The gang heads to Robin (Cobie Smulders) and Barney's (Neil Patrick Harris) wedding in this episode. However, they are forced to deal with personal circumstances that may alter their lives. Sherri Shepherd and Wayne Brady guest star. CBS/Citytv, 7 p.m.
The Great Christmas Light Fight
Families compete to create the most dazzling holiday displays for the chance to win $50,000 in this premiere. Featuring judges Michael Moloney and Sabrina Soto. ABC, 8 p.m.
David Letterman: Stephen Colbert, Ian McKellen
Jay Leno: Simon Cowell, Megyn Kelly
Jimmy Kimmel: Queen Latifah, Cage the Elephant
Craig Ferguson: Demi Lovato, Louie Anderson
Jimmy Fallon: Amy Adams, Jack Johnson
Stephen Colbert: David Keith