During DayZ, when you have more than one item such as a primary rifle/shotgun, a pistol/knife, and a flashlight, you should be able to switch between the items. Such as this:

If I have a rifle in my hand, I should be able to "let it hang" in a front of body position and take my flashlight out if all I have is a handheld flashlight. If I have a headlamp style light, my character should be able to use his off hand to turn it on and off with a dedicated lights on, light off button.

Now, if I have a weapon mounted flashlight, and a head mounted one, I should be able to use the key to turn the weapon light on and off, and it should be the "primary light" even though I have a head mounted one equipped.

Light is a big issue in a survival game like this, especially in complete darkness. It shouldn't take acrobatics to turn on/off a flashlight.