Standard dog tag (make sure it's the appropriate approved metal for the laser machine. Coated metals or anodized aluminum worked for us)
A small image or symbol you like
Laser cutting machine (Can be found at many locations such as TechShop. Just go to google.com/maps and look up "laser cutting")
Step 1: Editing Your Image on Illustrator
Open up Illustrator, and open up your image.
Go to Object > Live Trace > Tracing Options
You want to make it "Black and White" and click on "Preview" on the far right.
Then adjust the "Threshold" number until the image looks how you like.
Place the image you like in the dogtag template. You can either download one of these or make one yourself. (Or if you go to TechShop they can set one up for you). To make one yourself, just measure the length and width of your dog tag, place the hole on the rectangle and place your image inside, making sure your image stays contained within the length and width of the rectangle.
Step 2: Using the Laser Cutter
Make sure your align your laser's origin at the top left corner of your dog tag or the holder. Focus your laser using the focus gauge.
Go to your illustrator file and click on Print. In the properties section, adjust the settings on the laser machine so it engraves and not cuts through your material. Make sure the DPI is 600 and the speed/power is 90/70.
You can get more info on the laser machine here: http://www.paseman.com/public/NegativePoissonRatio/References/LAS101_techshop_laser_cutter_sbu_v2_7.pdf
Press "start" on the machine and watch the magic happen!
Remove the dog tag, and clip it onto your keys.
You now have an awesome new keychain.