Despite the prominence of Only A Flesh Wound in media, there are some things that even writers would concede as pretty fatal. For example, if a character gets shot in the head or stabbed in the chest, they're pretty much done for, hopefully with enough time to give a Final Speech before their death.
Unless of course, if they're the Determinator or someone as tough. For them, that little hole where their heart was supposed to be is just another chance to show off how Bad Ass they are. Even that is Only A Flesh Wound, and the guy that injured them, and is likely to be pissing in his pants right now, is about to receive a world of hurt. When this occurs in a climactic battle, you often see a My Name Is Inigo Montoya sequence.
Killing the character after their display of Heroic Willpower for extra dramatic effect is optional.
Note that Normally I Would Be Dead Now applies only to things that would have killed a normal character even by Hollywood rules. If it's "merely" something like severe bleeding from the shoulder or leg, that's Only A Flesh Wound.
Surprisingly, this is actually a case of Truth In Television. There are many real life examples of people who had things rammed through their chests and heads and still lived due to the foreign material miraculously missing vital organs. This means there's a fine line between this and mere aversion of Instant Death Bullet. However, it's far more common in fiction than in Real Life and all of them were left incapacitated or unable to move, so Dont Try This At Home.
May overlap with I Can Fight.