crescent kicks

[YouKnowWho]

I've never really found that much use for it.

You may only look at crescent kicks from the offense point of view. Both kicks have value in defense application.

The waist level outside crescent kick can be used to escape inner hook (Ouchi Gari) that your opponent uses his leg to hook your leading leg from inside. In the following clip, all you need is to use your left outside crescent kick to move your left leg out of your opponent's right leg attack.

http://www.judoinfo.com/images/anima.../ouchigari.htm

The waist level inside crescent followed by side kick can be used to deflect a incoming front kick. You then kick back on his standing leg. This way you don't have to use your arm to block his kick and leave your head open.