Babel On! passes along the rumor of a leaflet from the "Iraqi Resistance" which orders surrendering "Invader troops" to lay down their arms, kneel 50 meters from their weapons, etc. In other words, a re-addressed surrender leaflet from the beginning of the war. I doubt it's from any actual guerilla groups. The only insurgent I've ever heard of with a sense of humor was Sub-Commandant Marcos, and it's hard to tell if he was kidding or just nuts.