WiiWare

Brand: Various Developers, Licensed by Nintendo

Product: WiiWare games (see list on Wikipedia)

Summary: Download games onto your Wii via an Internet connection, such as Defend Your Castle, TV Show King and Dr. Mario Online Rx. Requires a purchase of Wii Points, either in Wii 2000 Points Card form or directly from your Wii.

Price: Between $5 and $10 or more dollars, in Wii Points. The Wii 2000 Points Card costs about $20.

Obviously: Requires a Wii.