Bram Lambrecht is machining these aluminum keychains in the shape of LEGO bricks. They even clip on to official bricks. He sent me one engraved with the Boing Boing logo and it's quite luverly. (I'd show you but for some reason my DSLR isn't talking to my Mac right now.)
The basic brick costs $12; engraved text is $6 more.
Product Page [Shop.BLDesign.org]