Without having read the thread before I voted and responding to my interpretation of "What is the most important role a handgun serves?", I voted for "Duty, LEO, etc (to mean armed forces as well)". I believe that because a handgun is most important when being used for good (LEO, when its actually employed) and in AF use because it is helping the AF's and serving our country, etc.
I would have voted for "protecting life" in a general sense as the above is essentially what it does.
However, I would have voted for the more vague "Protecting Life, Liberty, and the Pursuit of Happiness" I.E. CCW, LEO, AF, HD, and others as well.