Here's an interesting article on how to use a knife (or, by extension, other weapon, including firearms) successfully in a serious situation. It's not about technique, it's about attitude. Not "Look at me, I'm a tough guy, aren't you scared?", not "see my flashy moves", just go ahead and put him down. If you read some of Miyomoto Musashi's duels, you'll see the same thing. The usual procedure was that the duelists would square off, recite their lineage, announce their challenge, and posture. Musashi would run right up and attack on the run. Often one blow was enough to finish the opponent.
Or to put it another way: when the bad guy get the drop on someone, he doesn't just shoot; instead, he holds the ambushee at gunpoint while he makes a speech. Don't be a bad guy.
By the way, an amusing bit from that article: "Lesson number one...if, in a physical confrontation, an old fat man ever asks you if you are ready, you are going to learn a very unpleasant lesson."