Avis pits horsepower against the economy to promote its car rental service. In the spot, from Interpublic Group of Cos.' McCann-Erickson Worldwide, New York, an announcer switches from "Buy" to "Sell" over pictures of a bull and bear. "Aw, heck, just rent," he concludes. "In an economy that's not trying very hard, we try harder," he says as the bear waves goodbye. Art director: Kelly Girth. Copywriter: George Dewey.