The alligator! Check out this story about a battle between an alligator and a Burmese python, the latter having come to be wild there via owners tossing them out (morons). According to the article, Burmese pythons have been thriving in the Everglades for 20 years, and could challenge the supremecy of the alligator, but they haven't won one yet. This, apparently, was the 5th recorded encounter, and in all cases the alligator either won, or it was a draw. Now sure, one could argue here that both lost, but since we are talking species vs species here, not individuals, the gators remain champ with the draw.
Thanks to GrrlScientist for the heads up on this one.