Found this at http://archiveofourown.org/works/678042 by Improvqueen

Sherlock Holmes was just a man
But such a man that never was
Some say best in all the land
Others say he was a fraud

Watson lived with Sherlock Holmes
At 221b Baker Street
Together they unburied bones
And from them solved their mysteries

But Sherlock had an enemy
His match in wit and cunningness
Maniac Moriarty
Loved to play his games of bets

Once they met the game was on
Good and evil plotting again
On a rooftop to act upon
Each played his best hand

Low and behold, the darkness fell
Moriarty played his final card
Gun to his mouth, toll of the bell
Ended the man of wit and stealth.

But with his final breath he took
The key to life for Sherlock’s friends
Only his own life forsook
Would halt the triggers being pulled

So with his final breath he called
John to tell him of his lie
Upon the rooftop edge recalled
His brilliance from his friends own mind

Standing now upon the stone
Sherlock took just one last look
His life he took upon his own
A step into oblivion

But John could not be convinced
Of his friends misdeeds and lies
And so by his grave he winced
“Please Sherlock don’t be dead.”