Floor Wipers

These give you an isometric chest and tricep workout (where the muscle is under tension but remains static) as well as an ab workout. The video shows this being done on the floor, but I often just do it on the weights bench because otherwise if my chest is already tired I can't get the barbell up (you need a certain amount of weight on there to provide the necessary counter-balance.) It can be a challenge to balance your body on the weight bench, but this forces you to make the movement controlled, which is no bad thing.