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".
In BattleTech when the Clans invaded, on the planet of Twycross, a single mechwarrior defended a huge chasm from the entire army of invaders. Of course, it helped that the entire canyon was rigged with explosives so that when his mech was destroyed, the whole thing collapsed and buried everybody.
