I'm submitting this because I keep trying to jinx people, and they either don't know what I'm talking about, or stubbornly refuse to stop talking until I say their full name.
So, this is the deal, right? If we say the same thing at the same time, I get to say jinx. And that means you can't talk until I say your name. If you do talk, I get to punch your arm. OK? So don't look all hurt and angry when I punch you. You broke a jinx, you deserve it.
Consider this posting a formal notice, served to the world.

And another thing, if I ask you a really easy question, then say the answer at the same time, then shout JINX at you, don't say "well why did you ask me if you know the answer, and why did you just shout jinx?"
Because if you DO say that, you'll be talking whilst jinxed, and by GOD, I will punch you. (In the arm.)

The jinxee, during the jinx, has the lifeline of escaping the curse of silence by anticipating what the jinxer is going to say and saying the same thing, negating the original jinx. This is more difficult when jinxed because you can't feed questions which might produce predictable results, and if you get it wrong, you get punched. The consequence of this rule is some pretty surreal conversations between the non-jinxed as they try to avoid saying anything that could be remotely guessable. This is also abusable by the original jinxer;
What do you call those people who make bread? Oh, now I remember, and I'm going to say the word after three. 3. 2. 1.
Jinxee, being stupid, says baker.
Jinxer says 'Jeff' at the same time and punches jinxer.

'American Jinx (Touch Wood)'
A slightly more complex version of jinx. when a jinxing opportunity arises, shout 'american jinx, touch wood'. The first person to find some wood and touch it may punch the other person on the arm. Normal jinx rules then apply.

French Jinx
I have it from a very reliable source that when a jinx arises in french playgrounds they say "you shall be cuckolded before I".
Nobody wants to be cuckolded - not because it's the fearsome prospect of being married to an unfaithful wife; more because it sounds like it's got "cock" and "hole" in it, and is therefore referring to the fearsome prospect of your unfaithful mum.

Double Jinx, Padlock Jinx
If both children say 'jinx' at the same time, then one can declare 'double jinx', requiring the first and last name of the jinxee to be spoken to break the jinx. If both children say 'double jinx' at the same time, this opens the 'padlock jinx', which requires the full name, including all middle names, to be spoken before the jinx was broken.
No-one really bothers with Padlock Jinx, as most people would rather take a beat in the arm than wait until their full name is spoken, especially if their middle name is Adalard, Swimbank or Cakbot2000.

Girls are shit at jinx, because they refuse to stop talking when you jinx them - about the new range of Scrunchies in Claire's Accessories, 87% of the time - and act all gay and go "ow" when you punch them in the arm.
Has anyone else noticed that "ow" is "mo" upside-down? Proof positive. Poof positive. Poof HIV positive. Like your dad. - Log