Nintendo costumes in Overwatch would be a no-brainer if I was part of Nintendo's upper management (and the game was definitely coming).
Mario = ????
Peach = Mercy
Link = Genji
Samus = Pharah
Donkey Kong = Winston
Ice Climber = Mei
And probably more I'm not clever enough to think off. After Bayonetta 1 and 2 anything goes really.
Shy Guy = Reaper
R.O.B. = Bastion