Who doesn't LOVE burpees? This is such a great body weight exercise that can be modified in so many ways. You can also add dumbbells, ankle weights, and/or even a weighted vest to increase the intensity.
Iaido - This is a "soft" martial art. Basically, Iaido consists of learning "To Draw The Sword". It's harder than it looks and you haven't felt pain until you've been whacked on the arms with a bokken!
The "Line of Pain" concept. All the most effective pressure points used in self defense can be found in a straight line, down the middle of the body. with just a couple of punches, kicks or knee strikes, anyone can take down their attacker