Weak points don't always beget weaknesses. Take Section Z, for instance, one of the hardest games ever to be released for NES (yeah, we know, it was super easy for you and GamesRadar are all a bunch of newbs, blah, blah, blah). If you manage to survive until the end without smashing your controller through your parent's TV, you’re met what appears to be a fairly run-of-the-mill boss. Small? Check. Confined to one place? Check. Highly visible eyeball weak spot? Check and check. Except, as those lucky few who have got there will know, actually beating this thing without getting pummelled into oblivion is the furthest thing from easy.
I included Section Z's final baddie as a reminder that, like a handful of bosses on this list, weak spots don't always guarantee an easy fight. It can be an advantage, sure, but not all make for easy pickings.