Some oil companies utilize patents as tools to negotiate new deals. Some of the largest and most productive oil companies in Canada are Suncor Energy, Inc. (NYSE: SU), Enbridge, Inc. (NYSE: ENB), Imperial Oil, Ltd. (AMEX: IMO), Canadian Natural Resources, Ltd. (NYSE: CNQ) and TransCanada Corp. (NYSE:TRP). Suncor is the largest company, in terms of total revenue, in Canada.