There's been many wrestlers through out time, and not everyone gets to wrestle everyone. Could have been because they didn't wrestle in the same era or they just never got a match together!
My list:
The Rock vs HBK
HBK vs Brock Lesnar
Brock Lesnar vs. HHH
Bret Hart vs. Kurt Angle
Undertaker vs. Sting
Myself vs Stone cold
CM Punk vs. Roddy Piper
Randy Orton vs The Rock
Andre the Giant vs Big show
Stone Cold Steve Austin vs Cm Punk
Just a couple I thought of. Pretty sure these have not occurred, some I do think happened but in triple threat matches.
My list:
The Rock vs HBK
HBK vs Brock Lesnar
Brock Lesnar vs. HHH
Bret Hart vs. Kurt Angle
Undertaker vs. Sting
Myself vs Stone cold
CM Punk vs. Roddy Piper
Randy Orton vs The Rock
Andre the Giant vs Big show
Stone Cold Steve Austin vs Cm Punk
Just a couple I thought of. Pretty sure these have not occurred, some I do think happened but in triple threat matches.