Learn more about progressive BW leg training in Convict Conditioning:
http://goo.gl/IyTt3F
Sample routine:
10 pistol squats
30 lunges
super set back to back for 6 minutes.
Lunges and pistol squats are variations of the same basic movement. In general, lunges are easier than pistols since they usually require less strength, stability, and mobility. However, it's not quite so cut and dry, some pistol squats are easier than some lunge variations and vice versa.