Cross Fit / HIIT
If you still look pretty afterward, you didn't do it right
Cross Fit and High Intensity Interval Work-outs are awesome. They are a great way to improve fitness, give you that extra edge in your performance. They are also a great way to work yourself to the bone without spending all day on a bike or running the same route you always run. I am not a huge fan of Olympic Weight Lifting because so many people get hurt doing it, so a lot of these workouts are WODs or routines that avoid heavy squatting, jerking movements and power cleans. I'm not saying these are bad exercises, they just require perfect form or else you will end with a messed up back or neck.