[Zirro]

It's "Snow Leopard". Apple isn't running low enough on cats to have to resort to mythological ones just yet ;-)

[_delirium]

Hah, you are of course correct. I can never keep the order of OSX cats straight, so I had to look up which one 10.6.x was. But then I typed it out wrong even after doing so!

[niggler]

Unfortunately SL,L,ML doesn't suffice because Leopard (10.5) is also L :/

Though it should be noted that there is no other version that starts with 'S' ...