Lots and lots of Warhammer 40,000 fluff characters get scenes like this. Most notably, perhaps, Gaunt et al.
This can actually happen in a way in the actual game. Say you have a Chaos Predator declare Tank Shock on a squad of Veteran Guardsmen. They pass the morale check, then have the guy with the meltagun step in front of the speeding tank, and take a shot at it. If the shot hits, the tank slows to a halt in front of the heroic soldier. If the shot misses, though, what you have is affectionately known as "hamburger with a meltagun".
To an extent, this is what the "defender" tactical role in the fourth edition of Dungeons & Dragons is all about. Classes that fit this niche (such as the fighter, paladin, or swordmage) are designed to be good at keeping the enemy's attention focused on themselves so that their companions can do their own stuff reasonably unmolested.
In fact, he utility power that the paladin's Champion of Order paragon path grants at 12th level is literally named "None Shall Pass". It powers up the character's divine challenge class ability for one encounter so that it affects two targets each time it is used, rather than just one as normal.
The setting of The Dark Eye actually has a patron saint of this trope: Saint Thalionmel, the Lioness of Neetha. A priestess of the goddess of valor, she defended a bridge against an invading army that had so far smashed straight through any attempt to even slow them down. When she was finally overwhelmed, a sudden flash flood (believed to be a divine miracle) swept away the bridge, the invading army and her remains.