I often turn my water to the coldest for 5 minutes before I'm done showering. After a workout I target the nozzle at the areas I worked out and notice my muscles feel less sore the next day, and I feel I have more energy throughout the day and feel less inclined to be lazy.
Also I think after you wash your face with warm water, it's good to splash some cold on it. The warm opens to pores to wash out the dirt and oil, and the cold closes them back up.