In WWII they carved initals and sayings into their rifle butts. One troop even went so far as to hollow out a circle and put a picture of his girlfriend or wife in and then cover it with probably a watch crystal for her to be forever in battle with him.
In Vietnam they wrote sayings and calendared their helmets with the days left to go home.
Here in Afghanistan there's body ink. Most of the Marines I met immotalized their lost brothers. Some had several names tattooed on their arms with art portraying who they lost, to be carried forever. Gunny Schadle had his wedding ring tattooed so he always had his wedding ring on, even in battle.
Here is a beautiful work of art on Corporal Austin Hershaw. It gives new meaning to the 'art' of war.