Walking. It's simple but also an amazing thing to do. I try to walk outside once or twice a day. It helps clear and stimulate my mind. It also helps me get ideas and solve any problems on my mind.
When I worked in an office, I made it a point to walk around my floor or another floor once in a while to clear my head from being stagnate in my cubicle. Occasionally I'd walk down to outside the building and around the block. It helped so much mentally and to get a little physical activity as well.
I wish some of you would try this. Look at it this way: if smokers get to go out every so often, why can't you. Then again if you are a smoker, add a little walking around to it. Even better, if you have a meeting, get the people to go out for a walk around outside to talk. The moving will get the blood going, the fresh air will make you think better, and not being in the building my help people's moods during the meeting.
If I was a manager, I'd require all my workers to get up and walk once in a while to clear their heads and maybe solve that problem they have. I want to point out lunchtime walking or outside doesn't count. Lunchtime is personal time and no work should be thought of. This is during work time.