Right now it appears the last action of President Obama is the letter on Guantanamo signed yesterday. Ironically, the executive order for closure of Guantanamo was the 4th order of this president signed January 22, 2009.
According to the National Archive, his very first executive order (signed January 21, 2009) was on the subject of presidential records disclosure. It revoked the order by President George W. Bush that was signed November 1, 2001.
I have n0t taken the time yet to dig into the detail of changes, but may revisit this topic if POTUS 45 issues a new order revoking Obama’s.