The Trayvon killing and most other gun related deaths can be prevented by discouraging concealed weapons and allowing "open carry". Concealed weapons don't stop attacks or allow victims to avoid a potential attacker.
"An armed society is a polite society. Manners are good when one may have to defend one's actions with his life"
Robert Heinlein
"No free man shall ever be debarred the use of arms. The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government"
-- Thomas Jefferson, 1 Thomas Jefferson Papers, 334
"The very atmosphere of firearms anywhere and everywhere restrains evil interference - they deserve a place of honor with all that's good"
-- George Washington