I think Brydon called it the "Captain's Chair". The station where you support yourself on your forearms with your legs hanging. Either crunch your knees up to your chest or keep your legs straight and lift them up. The key is to curl your torso up like a crunch on the floor at the top of the movement. You can also do these with a twisting motion on the upward and downward movements.
Another one is to sit in a "V" position on the floor. Balance on your butt with your legs extended in front of you about a foot or so off the floor. Lean back and balance until you feel good tension in your abs. Keep your hands in a fighting guard position. From there you can alternate between these four variations. (1) Flutter the legs. (2) Spread the legs to the side then cross back over the center. (3) Alternate pulling one knee to the chest then the other. (4) Pull both knees toward your chest at the same time. Get a rythem going with these. Do one variation for 10 or twenty counts, then move to the next. Repeat and do as many sets as works best for you.
Grab a leather medicine ball and get in a crunch position on the floor. Extend your arms and raise the ball above your abs. If you have not done this before start by dropping the ball only. Target all different areas of your abs as if someone is punching you there. Upper, lower, both sides. Maintain tension in your abs as you execute each drop. Once you have progressed you can pull the ball into your abs with as much force as you can generate.
If you do these in addition to your other regular ab routines, your abs will be fight ready.