Brent, I'm not sure if you're being satirical or not, but in the interest of being clear, allow me to address the points you posted.
A president's power with respect to Executive Orders is limited to directing the enforcement of already existing laws. Because of this, a president cannot "EO away" anything that congress hasn't delegated him the power to.
With E.O. power, he may could ban the CC he so despises
No, he cannot. Congress has made no law addressing CC one way or the other with the exception of prohibiting it on Government property and schools. Because of this, the president has no power to regulate CC on non-gov't or non-school property.
And my ominous Mossberg 500 assault shotgun
So long as your Mossberg has no features that are already regulated by the NFA or '68 GCA, no he can't do anything with it either. The only guns that the president may have EO power to regulate or ban are those which fall under the NFA umbrella and/or those subject to the "sporting purpose" import test. NFA items are pretty clearly defined and I don't really see how the president could regulate them any more heavily than they already are without an act of congress. Likewise, the "sporting purpose" test has already been applied about as stringently as the law allows, so I don't really see the president being able to do much more with imports unless he gets an act of congress. Either way, a Mossberg 500 is neither an NFA item nor imported so an EO can't touch it.
Another concern that's been brought up is the importation of ammunition. The GCA of 1968 places limits on the importation of armor-piercing ammunition so an EO could theoretically affect AP ammo. However, AP ammo is clearly defined by federal law and pretty much anything that meets the definition is already verboten. The Russian and Chinese ammo import bans of the Clinton administration were not enacted via congressional act nor EO, but rather through trade agreements with the importing nations.
About the only meaningful gun control that I can see President Obama trying to accomplish through Executive Order is directing the ATF to revisit the "sporting purpose" test in order to broaden the 1989 Assault Weapon Import Ban. However, the ATF has already banned just about everything that they have the authority to via their various rulings.
It seems obvious to me that there are certainly more firearms that the ATF would like to ban, the Saiga 12 shotgun comes immediately to mind, but they've as of yet found an excuse to do so. Most will remember the potential shotgun features that the ATF toyed with banning a year or so ago. It was pretty obvious to me that the proposals were aimed at semi-auto shotguns like the Saiga 12, but even so it couldn't find any features of a stock Saiga that closely enough resembled an "assault weapon" feature to give them a sufficient excuse to ban it. Not only that, but the ATF also got their proverbial hand smacked by congress for even considering further bans by section 541 of the Fiscal Year 2012 Agriculture, CJS and THUD Appropriations bills.
So, while the President might be able to take some gun-control oriented measures via EO, they will be limited to relatively minor ones. Contrary to what some people seem to fear, President Obama is not a king and he cannot simply wave his hand or strike his pen to paper and create sweeping, Feinsteinian (yes, I just made up the word Feinsteinian) gun control measures without the collaboration of congress.