Bosu
 

Much like the standard pushup, the BOSU variation is a great finisher that burns out the pectoral muscles while simultaneously engaging various regions of the core. Place your hands on the sides of a BOSU ball and slowly lower your body towards the base in a 4 second count before bringing it back up again in a slow and controlled manner. This unique variation is a solid way to work the abdominals while improving stability and overall functionality.