#4 Roy Keane (1993-2005)
The Irishman's temper was both his greatest strength and weakness. It propelled him to the top as a snarling, tough guy midfielder but also led him into numerous feuds. One too many arguments with Sir Alex sent Keane tumbling out of the club in 2005, after Keane had publicly criticised his United teammates on MUTV (the club's media channel).
However, despite his acrimonious departure, Keane was a very effective player for United, even through to his final days at the club. All in all, he won 17 major trophies for the Reds. In a similar vein to Gary Neville, he made the most of himself in his career.
Like Neville, Keane was not particularly technically gifted but his reading of the game was excellent. He compensated for his lack of flair through his boundless energy and stamina and he simply just wore players down through sheer grit and determination.
Keane also had an eye for goal (51 in 480 appearances), particularly during his peak at the club (1998-2000) and was capable of driving United to victory through sheer force.
Many older United fans will fondly remember his performance against Juventus in the Champions League semi-final in 1998/99. Though he had been booked and would miss the final, Keane still drove United to a 3-2 win (scoring the first goal) with a captain's performance.
That showed what Roy Keane was about- putting his heart and soul on the line for the Manchester United shirt.