I'd have to go with the mumakil. Yes, they're evil and evil isn't supposed to triumph over good, but... but.. the ents are tree people, for crying out loud. Yeah, they hurl rocks and stomp on orcs pretty well, but all the mumakil would have to do is get out the matchbox or a few axes.
How about darth vader versus pre-flaming-eye sauron? Two guys in funky armor with big nasty weapons duking it out to the death! Tickets on sale for $27.50!!