#1: There is no such thing as an "assault weapon". It is a made-up term not unlike the "fiscal cliff". When the Violent Crime Control and Law Enforcement Act of 1994 was written (the law containing the Federal Assault Weapons Ban), the ban applied to weapons of certain cosmetic characteristics, some of which had little or nothing to do with how effective a weapon is. Some of these include a "folding or telescoping stock" and a "pistol grip". In essence, this was a ban on scary-looking arms.
#2: No "assault weapons" (See #1) ban would have prevented the Sandy Hook shooting. Adam Lanza used four handguns to kill others and himself, and nothing else. There was a "long gun" that he left in the trunk of his mother's car. After viewing the police clearing the weapon and from what I know about firearms, it doesn't appear to be an AR-15 - not that it matters since he didn't use it anyway.
*UPDATE* There is contradictory information about the weapons used. So, I am striking-through #2. Link.
#3: When the Constitution was adopted, there was no standing army. There was no U.S. Army (the Continental Army was disbanded in 1783) and there was no National Guard. Militias were made of local armed citizens. So when you read the 2nd Amendment ("A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed."), it's a hard to make the case that there is no constitutionally-protected individual right to bear arms.
#4: If all of the Republicans in the House of Representatives stood up and stated that they would absolutely under no circumstances raise the debt ceiling, the United States would NOT go into default. Default only occurs when the Treasury cannot pay the interest on the debt. Currently, the Treasury has more than enough funds to do this. Since the Treasury Secretary is a member of the Executive branch of government, we will only go into default if the President instructs the Secretary to stop paying the interest.
#5: There would be no debt ceiling debate if a federal budget was passed into law. The last time Congress passed a budget was in April 2009. This is due to the fact that the Senate Majority Leader refuses to bring any budget up for a vote (the House has passed a budget every year). This is also a violation of the law, as Congress is required to pass a budget every year. The debt ceiling is automatically raised when the government is "over budget" - but since there is no budget, the debt ceiling is reached and requires congressional approval.