I just got this one in the mail yesterday, a Droid 58 by Cool Fall, aka David Livingston. The Droid is a titanium carabiner that can be used on a key ring or at the end of a lanyard. It locks closed using a hidden stainless steel pin, and the lock is disengaged by depressing or lifting an external lever. O-rings on each side of the carabiner provide the spring tension that returns both the gate and the lock lever back to their original closed positions.
The "58" in the Droid 58's name stands for 58 mm, the length of the carabiner. I measured it at 2 3/8" from end to end (not counting the split ring pictured), and I think that is a great size for this device, because it is big enough to manipulate effortlessly but small enough to fit in your pocket with ease when you don't want to clip it to anything.
Although David has stated that the Droid 58 is designed to require 2 hands to open in order to prevent from accidental opening, I actually found it fairly easy to open and close one-handed as well with a small amount of practice. This is a good thing, IMO, because I don't always have both hands free when I want to clip something.
Overall, I'm quite pleased with the Droid 58. With its sturdy construction, secure lock, and user-friendly size, it is arguably my favorite carabiner that I have tried.