Is there a way to create a new tag with a scripting????

Questions & Answers
1

I'm trying to create a new tag with a scripting that when you play the game changes the tag to another one that doesn't exists and when you stop playing the game that tag disappear.

2

Try looking at this answer.

http://answers.unity3d.com/questions/9222/is-it-possible-to-create-a-new-tag-by-script

No, you currently can't.