I have a preference for 10180 lights on my keyring, but my favourite button cell light has got to be the photon freedom. While this isn't a new light or anything, I feel it deserves some attention. Also I've done a bit of round up of various extra "features" contained within the photon freedom interface.
http://keychainpockets.blogspot.com.au/2014/06/photon-freedom-review.html
http://keychainpockets.blogspot.com.au/2014/06/photon-freedom-review.html