The Birka Open Hand Pacifier (idea)

A self-defense technique tailored to protect the practitioner from the harsher forms of retribution specified by the Swedish penal code.

Rationale: IANAL, but as far as I know striking someone with an open hand in the Kingdom of Sweden is considered simple assault (ringa misshandel), no matter the extent of the injuries caused.
The interesting circumstance arises, that forcefully hitting your opponent on the face with the palm of your open hand is the technique to be favoured in a brawl, since a good hit will leave evident and lasting proof of your good intentions (your open hand) where it landed.

The execution is simple, allowing for a high rate of success unless you are in a drunken stupor:

• Standing at slightly more than one arm away in front of your adversary, take a step back with your dominant foot. It should be your right foot if you are left-handed. As you do this, raise your front hand slightly before you, as if to keep the opponent at a safe distance.
• Stretch your back arm away from your body, as if you wanted to pick something on a table about one meter behind you. Keep your eyes on your opponent at all times and look suave.
• Swiftly shift your weight over to your front leg, pushing your back hip forward by rising your back heel, as you swing your whole body around an imaginary vertical line going from your front heel to your front shoulder. This should cause your back heel to turn outwards somewhat.
• As you swing your body, raise your back hand, keeping the arm slightly bent at the elbow. This is important unless you really wish to dislocate your elbow or shoulder as you land your strike. Also, keep your hand open and your fingers slightly spread.
• Let your hitting hand connect with the side of opponent's face. This is quite a broad target really.

That's it, but mind that this is a surprisingly powerful technique, and that you may cause your opponent permanent injuries.
While you shouldn't hesitate once you decided it's time to defend yourself, consider that having experienced the feeling of somebody else's body parts breaking under your bare hands might haunt you for a long time.