Obligatory safety information: Don't cut yourself with scissors, poke yourself with the pointy plastic corners, pinch yourself in the keyring, gouge yourself with the drill, burn yourself while singing the edges, obliterate yourself by jumping in front of a dump truck, or sue me after doing something dumb. If you read all this, kudos to you, because I didn't.
Step 1: Getting the Stuff
-Plastic Sheet. The piece I used was a binder divider in a previous life. It's fairly thick, stiff stuff...five hundredths of an inch, or 1.5mm.
-Key ring. Pull one off a crappy promotional keychain, buy some at the hobby store (shudder), or snitch them off an unsuspecting victims keys.
-Scissors. Tough ones that can handle the plastic. Unless you have a laser cutter. You could use a bandsaw, I guess...
-Mailing labels. The Smithsonion Museum of the American Indian is kind enough to occasionally send me these ones with uber-cool designs on them. Don't bother with the labels if you have the aforementioned laser, as then you can etch it.
-Pointy thing. I used a 1/8" drill, you could use a hefty hole punch, a hot nail, that laser cutter...