You pick out a large high-caliber pistol and charge it to your credit card, becoming a new gun owner without having to pass any kind of background check or even show your ID. What an absurd dream! You exit the store with your new firearm and...realize you didn't buy any bullets.
You exit the store again with your new firearm and some ammunition. You're ready, or at least as ready as you're likely to get. From here you can take a proactive approach to your defense or one that's more...well, defensive.