Johnlock in :
the adventure of the two stain
in this case we note that ACD hint at Watson's appreciation for men , and openness to admire beauty and elegance with his artist's eye regardless of the gender , which is , back in his time , quite unusual
while he never missed emphasizing on his deeper fascination and admiration with/of Sherlock's wonderful eyes
he often refers to them as keen eyes , grey eyes , wonderful eyes , ect
(or his hands , and long legs , and sinewy neck )
Ah ! the famous " the fair sex is your department " ;)
still in the adventure of the two stain , Watson's so called marriage approaches whilst Holmes sneakily and so subtily trying to infect his mind with suspicions , and trying to make him doubt his choice
why ? well it could be because of his geniune concern with his best friends hasty choice ,
or the more plausible hypothesis is because he wanted to keep him to himself , Holmes displays his possessivity toward Watson throughout the canons shamelessly , and likes using possessive pronouns " my boy , my watson , my friend , my boswell , ect "
moreover he knew the real motive behind watson's marriage and its not out of love , thats for sure , he knew he was trying to get in line with their societal expectations because of watson's high sense of morality and conscientiousness , remember that being a bachelor , living with another bachelor of the same sex , it wasn't very well perceived in Victorian society , and it may rise a fair amount of questions , and Watson, knowing his temper would be damned before judged badly by people , as opposed to Holmes who dont care about how people judge his style de vie .
