A rotating crunch that works the front and sides of your core at once. Slow and controlled beats fast and sloppy every time.
Every move in Core Buddy has a video like this one — and it builds the whole session for you, timer and all. Free to download.
The bicycle crunch with your feet on the floor. One leg moves at a time and the twist stays. Work with this version for as long as you like — when the full one feels within reach, give it a go.