Beginner:
Hammerfist - forward, down, side
Front kick to groin
combo: front kick to the groin, hammerfist (down or forward)
Knees
Choke from the side

Intermediate:
Defense vs hook - extended/covering
defense vs uppercut
Hair grab from the front

Advanced:
Axe kicks
gun from the side, in front of arm
gun from the front, pushing into the stomach