I love leg locks, but they are by far the scariest set of submissions around. Most of the time you are either caught completely off guard (no pun intended) or you can slowing watch yourself tapping as the inevitable happens. While you can always counter and defend leglocks, I believe that escape counters are even more plentiful than defenses. Nothing can change or influence a grappling game or guard game like the threat of leg locks. Regardless of there negative stereotypes, leglocks are just as classy as any other submission, don't take my word for it, just listen to the Classy Grappler.
Check out this sweet reverse grip ankle lock variation from the Classy Grappler.