Rocky vs. Rocky
Bullwinkle vs. Bull Shannon
Dark Helmet vs. Darth Vader
How about Ash (Ketchum) vs. Ash?
Veronica Guerin vs. Vito Corleone
Jason Bourne vs. Napoleon Dynamite
Brick Tamland (Steve Carrell’s character from Anchorman) vs. Barb Wire
Richard Nixon vs. Barbarella
Ash vs. Ashton Kutcher.
Bruce Lee VS Sara Lee
Miss Piggy vs. Bruce Lee.
Bride of Frankenstein vs American Gigolo
The Birds vs Nicolas Cage
We all win that one!
The Meteor from Armegeddon vs the Teletubbies.
The wood chipper from Fargo vs Snuggles the Fabric Softener Bear
Leatherface vs. The Brady Bunch
Darth Vader vs. Wesley Crusher
And I was going to say the Raptor and T. Rex in Jurassic Park vs. Barney
Oooh, good one!
Enzyte Bob Vs. Lorena Bobbitt.
I like actors fighting themselves:
Gwen DeMarco (from Galaxy Quest) vs. Ripley (from Aliens)
Peter Venkman (Ghostbusters) vs. Garfield
The Terminator vs. Mr. Freeze vs. Governer Schwarzenegger 
reminds me of the banned advert for the N64 game “BattleTanx”
Commercial opens with a Snuggle-esque teddy bear (Treddy) falling into a basket of towels
“Wheee!”
cut to a scene of Treddy on top of the dryer, saying in a cutesy voice
“For the Brightest colors, always use…, What the!..Uh-Oh!”
jump cut to a picture of an M-1 Abrams crashing thru the wall and sending Treddy flying towards camera, screaming
Announcer starts describing game, mixed with 3 cut-aways to Treddy…
1; running from the tank, with a close up shot on the treads, the tank fires it’s cannon
2; Treddy running towards the camera, left arm missing, right arm on fire, stuffing protruding from his body, the tank on his heels
3; Treddy lying in a tread path of the tank, tread mark across his chest, his left leg twitching involuntarily, right arm missing, he says, weakly “BattleTanx” and coughs up a stuffing-ball
apparently the makers of Snuggle fabric softener didn’t like the advert and wanted it pulled from the market, unfortunately the 3DO company caved and pulled it
(i have a copy frittered away somewhere on my pile of backup CD’s)
It’s not lopsided if Batman is prepared!
How 'bout a few cute animal ones?
Lassie versus Cujo
Benji versus Shardik
Flipper versus The Loch Ness Monster (or Jaws)
Skippy the Bush Kangaroo versus Shere Khan
Stuart Little versus Scar
Jar Jar Blinks vs KOS MOS from Xenosaga (Well, Jar Jar is a Gnosis.)
Thumper vs. ROUS
Buttercup vs. Buttercup
Montoya vs. Ramirez
Brock Sampson vs Aeon Flux
That’s just sick and wrong.
“I’m going to legislate you.”