The Supreme Court of the United States, in 554 U. S. ____ (2008) DISTRICT OF COLUMBIA v. HELLER [PDF], has said (quoting from the syllabus (headnote) of the Opinion):
The Second Amendment protects an individual right to possess a firearm unconnected with service in a militia, and to use that arm for traditionally lawful purposes, such as self-defense within the home.
The handgun ban and the trigger-lock requirement (as applied to self-defense) violate the Second Amendment. The Districtâ€™s total ban on handgun possession in the home amounts to a prohibition on an entire class of â€œarmsâ€ that Americans overwhelmingly choose for the lawful purpose of self-defense. Under any of the standards of scrutiny the Court has applied to enumerated constitutional rights, this prohibitionâ€”in the place where the importance of the lawful defense of self, family, and property is most acuteâ€”would fail constitutional muster. Similarly, the requirement that any lawful firearm in the home be disassembled or bound by a trigger lock makes it impossible for citizens to use arms for the core lawful purpose of self-defense and is hence unconstitutional.
Read the PDF for the actual opinion, taking note of what is not covered, such as registration, gun-free areas, etc.
Wikipedia has an extensive entry on firearms.
Also see Happiness is a Warm Gun.
image: Bobbfwed, HK USP 45.jpg, Wikimedia Commons