Darkness
Just finished reading Descending Darkness by Harry Turtledove, which is rather relevant here I think. The Darkness series is approximately WW2 redone in a fantasy setting - dragons instead of planes, ley-line caravans instead of trains, "eggs" instead of bombs, "sticks" instead of guns. I don't know how sticks are powered in times of peace, but in war, soldiers either A) kill captives for their life energy of B) some of the soldiers sacrifice their life energy to help their comrades keep fighting. Sticks "blaze" people - they fire beams of energy (lasers? they can be attenuated by water...).
So, if you want a system with ready access to your gun-equivalents, with the chance for some heroic-sacrifice/geneva-conventions-violations, and this inspires you, use it. If not, look at one of the other fine posts.
And read Harry Turtledove.