Keychains for single keys are a pain in the butt. Scott Amron's new Carabiner Key lets you just latch a spare key onto whatever the hell you want to latch it onto without going through hassle of an extra link.
The carabiner keys are functional blanks, so you can take them to a locksmith and get them fitted to your locks. It's not quite as Xzibity as Amron's Keychain Key, but the carabiner spares you (me) the embarrassment of being unable to open a simple keychain. [Amron Exptl]