Stephan Kesting wrote a nice article on Leglocks in MMA for his awesome Grapplearts Blog. Stephan is a big advocate of leglocks for both sport and self defense and includes some solid insight.
I am glad he mentions one of my favorites; Imanari who is a beast when it comes to leg attacks along with his training partner Shinya Aoki. If we look at the grappling end of the competition spectrum we have folks like Dean Lister, and Reilly Bodycomb (whom Stephan has a picture of on the bottom of the his blog post) both known and feared for their leg locking abilities:
For those of you thinking about competing in the advanced divisions of Ivan’s submission wrestling tournament, GSUBX, make sure you are savvy on your leglock defense for all submissions are legal including heel hooks!