Continuous curves (CC), IMHO, is an invaluable technique for any machine quilter. It is so simple yet so versatile. It can be doubled or even tripled for a more intricate look.
Another variation is commonly known as the Terry Twist which, while similar in execution, gives a completely different look.
Diana Phillips also expanded on the idea with her "Line Dancing" designs. Executed like continuous curves but with lots of interesting variations to switch things up a bit.