Bills passed by Congress and enacted into law are literally signed by the President; somewhere there is a physical piece of paper that Obama marked with a pen -- except in a few cases where it was a robotic pen: http://content.usatoday.com/communities/theoval/post/2011/11...

And the other decisions mentioned above come directly out of the office of the president, which is to say Obama and his cabinet and staff. The executive branch is the president's instrument to wield; I think everyone would agree that the president has responsibility for the actions of his appointees and White House staffers. And the key documents like executive orders are, again, literally signed by Obama's hand.