Insurance: for the biggest things. Health, home, car. Mainly because the government doesn't provide much protection for disasters and other crises.

Guns: I don't know personally because I have no interest, but I think there's usually (or at least often?) a waiting period. And yes, they're sold at Walmart but not at other general/non-sporting goods stores.

Flossing: You don't have flossing? Why didn't I know this? You take a piece of wax-coated thread and slide it between your teeth, it pulls out bits of food that brushing misses, also keeps your gums healthy.