Don't have a lot of time for a workout? No equipment?
As you get stronger, try this one.
It's just ONE exercise: the BURPEE.
Here's the workout called The Burpee Ladder
Do one, take a 30 second rest then go to the next set. Increase or decrease rest depending on your fitness level.
As you get stronger, you can increase the ladder and go up to 6. Or start reducing the rest between each exercise.
Don't let the simplicity fool ya.. it ain't easy.