Back when I used to tournament fight here are some tricky kicks that seemed to work for me:
Turn kick (roundhouse) to the head. Most people turn their hips and lean way back with this one. I had developed the ability to throw the kick from an almost straight up and down standing position and fairly fast (almost as fast as the average punch). So, the technique wasn't as telegraphed or expected as the normal "roundhouse." So I would time it to where as soon as the corresponding hand (right or left) would drop slightly below the chin, I'd pop it in there real fast. I mostly tagged people with my lead right leg. I could get people with this one who were very good, because it was so sneaky.
Twist kick to the abdomen, usually under the ribs. This is a good groin shot as well if you are allowed to strike there in the tournament. A twist kick almost resembles a front kick, except the knee twists outward. It snakes around peoples guard, under arms, etc., where the front kick just goes straight in. I would often pull this one off after a turn kick fake, or if my turn kick got blocked.
Hook kick to turn kick. The old bring the guard down with the hook kick, then slam them with the turn kick worked for me also sometimes.
WHAT DIDN"T WORK FOR ME: Cresent kicks and ax kicks didn't work for me in tournaments. Part of this might be because I was so short. I couldn't get the distence I needed for any of these because of my height, and If I was as close as I needed to be, I risked getting my leg caught and ending up on my @$$.
The basic Front, side, roundhouse worked good for me also, and I found that as the contact got harder, I resorted to more simpler kicks.