Perfect shout.And Leonard-Hagler is another example of a fight that was a 116-112 if you're going on a must win scoring system. I love Barrera(my all time#2) and the Hamed fight is one of my all time faves,but the highlight reels don't tell the full story,and it was not the brutal beatdown some seem to recall.It's a classic example of the OP's question.
As has already been mentioned many times, the most obvious case is in fights where the rounds are easy to score, but the rounds won for each fighter ends up being close. Another possibility is when one fighter just edges every round. It's clear that they won, but the fight was very competitive throughout. These ones can get much more debatable, so the 'clear' aspect won't always apply.