This instructable is pretty easy to do, and lets you display your lego-ness.
All you need is :
1) a Lego mini fig
2) a small linked necklace chain (the kind with a clasp)
a 18 inch long piece of string that you like (cant be too thick)
Step 1: Get the lego minifig ready to go
once you are done that, position his arms straight in front of him
stick your thumb in between his arms, and push either way to pop his arms off