Steve Maxwell is an amazing martial artist and teacher. (I’ve trained with him, so I know what I’m talking about.) I believe he’s in his 60s, but he has the strength and agility of an above-average really in-shape 20-year-old. He’s in demand all over the world as a high-level MMA, jujitsu, and general fitness trainer.
If you’re interested in some down-and-dirty street fighting techniques, you might find his video catalog helpful.