How many of you own a gun ? What are the requirements in order to legally own a weapon in the US ?

I heard it depends from state to state. Also Texas is cool cause you can shoot any tresspasers. In comparison, in California it sucks cause you cant shoot him if he's not a threat to you or you family even if he is on your property. Meaning if he robs you and you find him and he starts running, you cant legally shoot the beep out of him to stop him from going away with your belongings.

Correct me if i am wrong. I'm only talking from what i read.

P.S. If you own one, have you ever been in a situation of using it ?