It is because of their ability to allow all individuals to protect themselves that makes guns such a great invention. With a gun, a 90-pound grandma can protect herself from a 200 pound assailant. Guns are the ultimate leveler of the playing field. Note that in every state in the US that has enacted concealed carry laws, crime has decreased dramatically.

But I won't use statistics to make my point because that would make it too easy -- the actual statistical evidence (as opposed to media factoids) is so overwhelming.

No 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 the tyranny in government.
Thomas Jefferson, June 1776

The last and most important check on government abuse of individual rights is an armed populace, thus the second amendment. A written constitution requires somebody to enforce it. Any mechanism built into the government, such as Checks and Balances, can be eventually bypassed by a determined government. Ultimately, the only thing that can prevent the use of force is the threat or use of greater force. To this end, the people are the ultimate check on government.

Only an armed population has the ability to overthrow a tyrannical government. Governments are well aware of this. In every dictatorship, ownership of guns is outlawed to the general populace. Before the Nazis went about exterminating their Jewish population, they needed to disarm them first. A state treads carefully when the citizens are armed.