President Barack Obama KILLS at the White House Correspondents' Dinner

Sarah Palin, Mitt Romney and Hillary Clinton were all on the receiving end of shots from President Barack Obama at last night's White House Correspondents' Dinner.

Obama seemingly began the night on a serious note, touching on the one-year anniversary of the death of Osama bin Laden ... but then the video screen showed a picture of Donald Trump.

Host Jimmy Kimmel's routine was a bit more polished -- poking fun at the Secret Service prostitution scandal, Obama's re-election bid and, of course, Kim Kardashian.