You know the drill: Head to the Mozilla.org website and get downloading! But this may be the last time you need to manually refresh Firefox, thanks to version 15 adding the ability to download stealth updates in the background.
Odds are you're a good person. You go to work, pay your bills, assist the elderly across the street, and get to bed at a reasonable time. So why would you want to be an amazing Renaissance-era assassin, leaping from a nearby rooftop to quickly dispatch your target with concealed wrist blades (or any other weapon), quickly looting the body and escaping without a trace?
Because it would be about the most fun you could have on your Mac.