I worked in wine retail for a time and have seen plenty of 'em. +1 for the waiter's 2-step, aka "broken knee." I have a 1-step laguiole with a teflon-coated screw that I love because it's sexy and perfectly weighted but frankly not as easy to use as a two-step.

The rabbit-style things I hate. Ditto the CO2-powered ones- they ALWAYS spray!