Real men use their teeth though.

(I never opened a bottle that way; but I did see someone break a tooth once. A molar, clean in half. Not sure if I'd rather have a wire stuck in my gut or break a molar in half.)

I have opened beer bottles with my belt buckle. Apparently this surprised people.

...I have seen someone successfully open a wine bottle with a shoe.

Cap of another (unopened) bottle works perfectly for this.

if you have sturdy (ie like volkswagen/audi/bmw) keys, you can use a key in a similar fashion

Bic lighters are exceptionally good for this (one of the important life skills I learned in college).

Can't speak for BMW keys, but every VAG key I've had has been horribly flimsy. Don't use it to open bottles or you'll be locked out of your car.