Against a southpaw or orthodox opponent?
Against another orthodox opponent, there are inside leg kicks that will off balance your opponent. You can also do a power switch kick to their rear quad. It's awkward and takes a good angle to pull it off, but it hurts like a son of a bitch if you nail it. Most people don't condition their rear leg to take kicks like their lead leg.
EDIT: Here's an example
Against a southpaw opponent, you can pull off a lead leg kick, but you need a good angle to pull it off with any power. The rear leg kick to the inside of their lead leg is usually wide open, though.