A standing desk plus a soccer ball (or the like) to put my foot on. The desk encourages me to move around which keeps me more alert, and the increased circulat

A standing desk plus a soccer ball (or the like) to put my foot on. The desk encourages me to move around which keeps me more alert, and the increased circulation keeps my brain feeling more active. By propping one foot up on the ball my posture is automatically put into better positioning allowing me to stand comfortably for longer periods; and it allows me to fidget a bit as well. Staying active and alert like this makes me significantly more productive.