KILLER Rotational Core Training - Upper Body Push-Pulls
http://www.powerfultrainingsecrets.com - this is one of my favorite core exercises. It works back, chest and hits the deep abdominal muscles extremely hard. You're doing a 1 arm dumbell bench press and a 1 arm cable pulldown simultaneously. The cross-tension goes right through the core, which has to stabilize for both movements. This one is a serious eye-opener the first time you try it!