Basically, all the "unusual" combos I know involve throwing a kick, missing it big (essentially telling them to start moving in), but then following it up with something big to catch them as they come in. You could throw a crescent( whatever its called where you throw essentially a round house to the head, and let it bring your body 360*) kick, then follow it up with a second.

If you're a big leg kicker, throwing a lot of leg kicks all fight, and then, late in the fight, throwing a "Superman Punch" (as they call it in the UFC, not sure of its actual name...basically, you chamber a roundhouse kick, but convert to a jumping, overhand right in one smooth motion that goes right above their guard) tends to work nicely, but only once. Make sure you put a lot into the punch, because it will only work once, and you really need to catch them for it to be effective.

Most of the combos you dont hear about, you don't hear about because they dont work very often, tend to be gimmicky, and are easily recognizable and hence, avoidable. Don't try any of these combos often, throw it out maybe once right off the bat, or late in the fight, once your opponent has become used to the way you fight, and expects you to do a certain thing.