Muhammad Ali v Joe Frazier III
The first encounter between the two then-unbeaten heavyweight greats was dubbed "The Fight of the Century" and more than lived up to its billing, as Frazier decked Ali with his murderous left hook in the last of 15 pulsating rounds to seal a unanimous decision win. Ali levelled their personal series at 1-1 in New York in January 1974, outpointing Frazier in a non-title bout after which both men were viewed to be on the slide. 'The Greatest' then stunned George Foreman in Zaire to set up a clash for the ages in Manila.
Ali opened up an early lead but Frazier, fuelled by a furious anger his long-time rival's persistent barbs had caused, made the middle rounds an ordeal for the champion. A brutal contest took its toll on Frazier, however, and a long-standing issue with his left eye and the swollen features caused by Ali's blows meant he was badly beaten in near-blindness during rounds 13 and 14. At that point, trainer Eddie Futch had seen enough, famously telling is man: "No one will ever forget what you did here today."
'Sugar' Ray Leonard v Thomas Hearns II
Like Ali and Frazier, Leonard and Hearns' first bout for the unified world welterweight championship in 1981 was a highly anticipated global event that thrillingly lived up to the hype. Sugar Ray was down on the cards before pulling a stoppage out of the bag against an exhausted Hearns in the 14th round.
Almost eight years and their primes had passed by the time they met again up at super-middleweight for the WBC and WBO belts in Las Vegas, but two era-defining fighters served up a classic. Hearns sent Leonard to the canvas in round three thanks to a chopping right cross, with that honey punch also helping to floor his weary foe in the 11th. Leonard rallied in between times but even accepted himself that the draw returned on the scorecards was an unfair reflection on Hearns' work.
Roy Jones Jr v Antonio Tarver II
Jones cemented his status as an all-time great by smoothly outboxing John Ruiz to claim the WBA heavyweight title in March 2003, becoming the first former middleweight champion to clinch a heavyweight crown since Bob Fitzsimmons in 1897.
Dropping back down to the light-heavyweight limit after that historic feat proved problematic for Jones, who laboured to a controversial majority-decision win over Tarver later that year. A rematch the following May came after Jones failed to secure a super-fight against Mike Tyson and Tarver shocked the world by obliterating his opponent with a counter left-hook in round two. Jones would lose the rubber match on points and was never the same fighter again.
Manny Pacquiao v Juan Manuel Marquez IV
No stranger to multi-fight sagas with Mexican greats, Pacquiao beat Marco Antonio Barrera twice - either side of his initial disputed draw with Marquez - and twice avenged a loss to Erik Morales with stoppage triumphs. Marquez was down three times in that initial IBF and WBA featherweight title clash in 2004. Two subsequent points wins for Pacquiao failed to conclusively settle the argument, with his 2011 majority-decision triumph for the WBO welterweight title leaving a particularly bad taste for many fans.
When the duo squared off in Las Vegas a year later, a mutual desire to avoid the scorecards was clear. Marquez left Pacquiao on the seat of his pants in round three before touching down himself in the fifth. Bloodied, JMM seemed to be staring at a stoppage loss under Pacquiao's blurring fists before finding a thunderous short right had that left his in-coming rival face first on the canvas.