Bob gives Dave a good beating until the latter brings out a second knife and stabs him.
Dave proves to be better than Bob expected.
Double Subverted: Bob beats him anyway.
Parodied: Dave brings so many knives with him that he can't stand up under the weight.
Dave keeps pulling out knives, while Bob uses progressively more improbable barehanded disarms to take them away.
Barring occasional flukes or surprise attacks, the fighter with the superior skill wins, ties going to the one with the knife. Bob the Marinetrounced petty muggers coming at him with a knife using only his fists, kills unarmed fanatical cultists trying to do a Virgin Sacrifice with his combat knife, but loses to Vladimir the Spetznaz coming at him with a knife when he's unarmed. Charlie comes at Dave, both everyman, with a knife after his wife cheated on him with Dave, and easily wins. Every once in a while, an inexperienced fighter gets a lucky hit on an opponent who was way out of his league.
Averted: Knives and fists are about even, so no one's guaranteed to win based on their choice of weapon.
Enforced: "We need to show how skilled Bob is in this scene, so let's have him bring down a better-armed opponent with his bare hands."
Lampshaded: When Dave pulls out a knife, Bob points out that he's better at fighting with his hands.
Invoked: Bob gives Dave a knife, knowing that he's inexperienced with it and won't be as skilled barehanded.
Exploited: Bob is secretly Made of Iron and goes into battle barehanded against Dave, who is armed with a knife. Bob counts on Dave being taken by surprised, allowing for a quick win.
Dave throws his knife away before the fight.
Dave gets training in resisting and countering disarms as well as how to use his weapon properly.
Discussed: Bob explains how better-armed fighters get complacent and make mistakes.
Conversed: "Hey, this guy just pulled out a knife. Bet you he's about to get his ass kicked."
Deconstructed: Since he can't win in a fair fight, the next time they meet, Dave just shoots Bob from afar or stabs him in the back.
Reconstructed: Bob starts wearing body armor to even the odds when fighting barehanded.
Played For Laughs: Bob keeps a running tally of how many times Dave's brought a knife to a fistfight. "You're a slow learner."