That is the SAS knife.
88Update: White House press secretary denied reports that in attempting to unsheathe the dagger President Obama managed to kill three Girl Scouts, two of the press pool and wounded Joe Biden. Jay Carney further reiterated that none of the furniture was damaged by the slight mishap with the ceremonial dagger.
Reports that Obama later inadvertently stabbed himself then swallowed the Fairbairn-Sykes while trying to show off with it to his golf buddies are also greatly misrepresented.
When asked for comment Vice President Biden replied, Its not a big f*cking deal.**