What is a good defense weapon?

****Before reading post******: Please read note at the bottom I'm 20 y/o living in the state of California. I'm able to purchase a shotgun and assault rifle (10 round clip semi auto) but I'm not able to purchase a pistol. I have clean history etc. so I am able to purchase a gun. In your opinion, what... show more ****Before reading post******: Please read note at the bottom

I'm 20 y/o living in the state of California. I'm able to purchase a shotgun and assault rifle (10 round clip semi auto) but I'm not able to purchase a pistol. I have clean history etc. so I am able to purchase a gun. In your opinion, what is a good home protection gun? I was looking at m14, ar-15s are too much and not effective enough under stupid CA laws.... Any suggestions? experience is always golden.

***Note****: I don't care if you don't like guns, I'm using it for protection. Criminals will always have guns illegally and use it against civilians. I fight fire with fire. If you don't want to answer my question, don't leave stupid snaring remarks. You will be reported.
Update: @tringle,
In California, That's an assault rifle. As I've stated "under stupid CA laws.." and excuse my clip/magazine misuse.
Update 2: @ou8012,
Good for you. Not all 20 year old people are stupid and immature.
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