Im gonna have to go with
1. Hanging Leg Raises (side-middle-side)
2. Bicycle Crunch
3. Twisting Oblique Machine (actually my favorite but so many gyms dont have them, I put it at 3)
I'll have to go with the bench press...lol just kidding I'll go with the bicyle crunch. The bicycle crunch is where you lie down in the standard form of a regular crunch. You put your hands behind your head and you raise your legs with a 90 degree angle from your lower and upper legs. You rotate from bringing your left elbow to your right leg extending your right leg and Vise Versa.