#1: All-time top scorer for two different clubs

This has to be the toughest of all, considering Ronaldo's decision to leave the Los Blancos. A Ronaldo-to-Manchester-United rumour has been the highlight of every transfer window for the past few years.
Although the Real Madrid forward has pledged his heart to the Bernabeu, he would certainly relish being the first player to be a record goal-scorer for two different clubs.
With the record for most appearances for Los Blancos looking out of his reach, CR7 might as well try his hand at achieving this rare feat.
Of course, no player in the history of football has been a record goal-scorer for two different clubs. Ronaldo, on the other hand, has already become Real's all time top scorer and has 118 Manchester United goals under his belt.
Ronaldo's team mate and English international Wayne Rooney recently became United's all time top scorer for by scoring 253 goals.
If Ronaldo does decide to return to his beloved club, it would require him at least four seasons with his current goal-scoring rate to break Rooney's record at Manchester United.
The 32-year old would certainly have an upper hand in the eternal comparison with Lionel Messi as the best player in the world, if he achieves this rare feat.