Pressing "r" will unequip one's current weapon/s, which will help to run faster (less weight), and pressing "r" again will re-equip your weapons. I tend to use a shield 90% of the time, so this is really handy for me. It also helps a lot after swimming, as swimming automatically unequips one's weapons, so press "r" after leaving the water to re-equip the weapon/s you were using when you entered the water. This is also very handy when taming wild animals (boar, wolves, lox), as it is necessary to be crouching (left-ctrl) with no weapons equipped, when taming animals. Having ones weapons equipped near animals one is attempting to tame really agitates them.