I put tar on my wife's toothbrush
Are you being serious? That's a strange thing to do. How did she react?
She said she would leave me if I did it again.
It was really inappropriate of you to put tar on your wife's toothbrush because she could have been hurt if she used it. You should never do anything to another person's toothbrush because it's a very personal item.
I don't care, I'm going to continue doing it.
Don't you want to have a trusting relationship with your wife? She will trust you more if you refrain from doing these types of things.