When the ninjas finally track you down while you are at the office, how will you defend yourself? Why, using the "Survival Dry Erase Marker" (TM) brought to you by Lokotronix Labs: Survival Division. It looks like an ordinary marker, but in mere seconds it transforms into a steel-pointed fist of death!

DISCLAIMER: this is just an art project. DO NOT take it into your actual office, school, a plane, etc. It might even be illegal to make or possess where you live, check your local laws. I AM NOT RESPONSIBLE IF YOU GET IN TROUBLE.

Step 1: Fabrication

Materials:

Old dry erase marker or similar
2 Steel rods 2.5" x 3/16" or whatever you can find
A piece of steel bar, 4" x 3/16" and as wide as it will fit snugly inside the marker. I used 1/2"
A small round piece of of plastic (I used acrylic) about the same diameter as the marker

Procedure:

Carefully remove the back plug from the marker and all the innards. Save the tip in order to make a look-alike steel tip
Cut your steel rods to length (~2.5"). From the points and cut a thread on the back, ~1/8" long. If you have access to a lathe, leave a shoulder as in the picture. Note that the thread diameter will have to be smaller than the bar is thick in order to drill and tap the corresponding hole on the bar side
Use a hacksaw and a grinder to shape the steel bar. Make the tip as close as you can to the original. I used blue machinist's paint so it even looks like a real tip. Test the fit on the marker to make sure it sticks out as far as the original tip.
Drill the holes in the marker body and on the steel bar. Make sure they are aligned. Tap a matching thread to >1/8" deep. I drilled extra holes to free the bottoms of the threaded holes for convenience. For hole locations, grip the marker and make marks, mine ended up being ~7/8" apart.
Cut a thread the marker back with a suitable pipe thread cutter. Thread the round plastic piece correspondingly and test fit. Note: drill two small holes or mill a slot so you can screw it in and out with needle-nose pliers or a flat screwdriver
Using sandpaper (or a lathe :)) reduce the diameter of the back plug so that is fits freely inside the back of the marker. Screw in the plastic piece to the correct depth so that the plug goes in at the right depth. Take them off and glue both pieces with superglue or similar and test fit again.