Sweet Mother Earth! The magnetic lock collar is sexy as hell! Too much $$ for me though.
slavemira, I love the one your Master chose for you. How has the chrome plating held up?
These are pretty hot too:
Stainless Steel Collar
Black Anodized Aluminum Collar
And especially this one:
Steel Collar
Though, if you're thinking long-term, I'd go with something other than the cold roll steel one. The ad says it will rust. But then, part of the fun could be maintaining it and keeping it rust free. And there's just something SO sexy about the idea of plain steel around my neck... nothing fancy, just utilitarian. You know?