Famous rivals or competitors that never faced each other

Whether it's sports, combat, intellectual debate, etc., in many facets of life and competition, there often seems to be competitors or compatriots whom you'd love to see 'face-off' so to speak, but frustratingly never do. You want to see how their skills would match-up, but it seems it was or is just not destined.

What examples most come to mind? Here's mine:

Chuck Norris vs. Bruce Lee
Michael Jordan vs. Lebron James (different eras, but you wonder what would've happened if they were contemporaries)
Marciano vs. Mike Tyson

 

In B4 Floyd and Pac fans take over this thread

 

I would have loved to see a prime Gerald McClellan vs a prime Roy Jones Jr. on a professional level. They met in the ammys. That's just small time business though

 

leaping lanny poffo and randy mach0 man savage

 

Money/Pac Man
GSP vs. Anderson
Fedor vs. UFC

Those three make me a sad panda.

 

Ronda has surpassed Pac as Floyd's main nemesis

 

floyd/manny

 

Rogan ~ Snipes

 

Uncle Dana vs. Tito

 

Frank Shamrock and Sakuraba

 

Doesn't just have to be fights.

C.S. Lewis vs. Bertrand Russell in a debate on God's existence

 

Of course, prime Ali vs prime Tyson
And from pop-culture, I guess, Yoda vs Vader or Imperator Palpatine. I can't remember, I think he fought against one of them

 

Bert and Ernie. I swear they never faced each other, only the camera.

 

Fedor vs Lesnar

 

How about PBF vs Margarito?

Or how about Lennox vs Vitali for real?

Or Donald Brashear vs George Parros

Or Donald Brashear vs Milan Lucic

 

Rickson/Sakuraba in a no time limit match

 

Metallica and Megadeth

 

BHop and James Toney

 

One question I've had for a while - Did 'let me bang bro' actually get to bang in the end? Who was he looking to fight?

 

Bruce Baumgartner vs. Aleksandr Karelin in a cage match hell in a cell inferno boiler room brawl.