What's your recommendation for a keychain knife?   I'd like omething small, light, and easy to open.

The current version of the Spyderco Ladybug has a few advantages over the old model:

• The same VG-10 steel used for Spyderco's larger knives.
• An improved, more grip-able handle shape.
• Available with a black, white, orange, or stainless handle.

 
Böker recently released the KEYCOM, the smallest in a line of several excellent knives designed by Chad Los Banos.  It has AUS8 steel and a "frame lock" design.
 
The bubbly-looking Buck Transport has a less-lethal appearance, a blade which locks closed if you are the nervous type, and a bottle opener