L. Ron Hubbard vs. Jesus Christ
Tom Cruise vs. South Park
John Travolta vs. John the Baptist
And yet, here's a hysterical one:
thetans vs. midichlorians
More:
George Bush vs. Common Sense
Karl Rove vs. Truth
Dick Cheney vs. Careful Aim
Condoleeza Rice vs. Orthodontics
And lastly, here's one for die-hard Frank Zappa fans:
T vs. B