Cai Guo-Qiang: Head On could be seen at Deutsche Guggenheim, 2006 : link.
Head On concept:
With few wolves scattered in the front gallery, all ninety-nine wolves run, gallop, and jump toward the far end of the exhibition hall, where a wall stands. The bravery of the wolves is met head on by the unyielding wall. As the leading wolves go down, many more follow with force and determination. As those in the front fall and pile up, those behind take up their positions.
Meanwhile the Harvey Nichols "sale" ad called wolves created by Y&R Dubai won a Bronze Lion in Cannes this summer.
Omg I forgot, Hat tip Joelapompe, the Badlander-ninja. Wanna see twin ads? He's got'em.