I know exactly what you talk about - the front leg side kick. Its the foot jab of TKD. I believe the kick is thrown as a snap from the chambered position and at the milisecond before the impact, the hips are rotated. Its talked about in B. Lee's book "Tao of Jeet Kune Do". In the book, he also mentions the hook kick to the head, which is somewhat flashy but has power. Check out the video on the following page called TaeboKTFO. A guy delivers a hook kick in a point style tourney and knocks out Billy Blanks (before the days of Tae bo).
http://www.bullshido.us/dl_search.as...search=&num=30