ThinkGeek has this new pen out called the Uzi Tactical Pen. This ball point pen is made of aluminum and accepts Parker and Fisher Space Pen refills. Besides functioning as a pen, it can also protect you from bad guys, with the razor sharp crown at the top. It will definitely leave a mark and as an extra bonus, you can send the harvested DNA to a crime lab, and identify your attacker should he/she have a DNA sample on file.  Oh, you can also use it to break glass. ThinkGeek sells this writing instrument- slash- “crime stopper utensil” for $14.99