Choosing a handgun

A person is justified in using reasonable force against any other person to protect the person or a third person from what the person reasonably believes to be the imminent use of unlawful force. However, a person:
(1) is justified in using deadly force; and
(2) does not have a duty to retreat;
if the person reasonably believes that that force is necessary to prevent serious bodily injury to the person or a third person or the commission of a forcible felony. No person in this state shall be placed in legal jeopardy of any kind whatsoever for protecting the person or a third person by reasonable means necessary.
(d) A person:
(1) is justified in using reasonable force, including deadly force, against any other person; and
(2) does not have a duty to retreat;
if the person reasonably believes that the force is necessary to prevent or terminate the other person's unlawful entry of or attack on the person's dwelling, curtilage, or occupied motor vehicle.

Alabama, Arizona, Florida, Georgia, Indiana, Kentucky, Louisiana, Montana, Nevada, Oklahoma, South Carolina, Tennessee, Texas, Utah, and Washington.

California, Idaho, New York, Pennsylvania, South Dakota, Iowa, New Hampshire, New Mexico, Virginia, Vermont, and Washington, D.C.

Also, I found this..

states with STRONG Castle Doctrine and stand-your-ground laws include:

states with limited, little, or no castle law or case law giving citizens the rights to protect their homes using force include:

Dated July 2011, so somethings may have changed since then
http://source.southuniversity.edu/castle-doctrine-from-state-to-state-46514.aspx

Be sure to know and understand the Castle Doctrines in your state!