Which Exercise Machines work?

So many people will spend thousands of dollars on different kinds of work out machines. But which ones will give them what they want to achieve? You can buy your bow flex and ab machines but the one equipment that will never let you down is the treadmill. I have been successful using mines and it really was a good investment. You can sprint, walk or jog and burn calories. You are working your legs, your back and throw in some weights and work out your arms while you are at it.