"This is the farewell kiss, you dog!"

The Iraqi journalist, Muntader al-Zaidi, 28, a correspondent for Al Baghdadia, an independent Iraqi television station, stood up about 12 feet from Mr. Bush and shouted in Arabic: “This is a gift from the Iraqis; this is the farewell kiss, you dog!” He then threw a shoe at Mr. Bush, who ducked and narrowly avoided it.

As stunned security agents and guards, officials and journalists watched, Mr. Zaidi then threw his other shoe, shouting in Arabic, “This is from the widows, the orphans and those who were killed in Iraq!” That shoe also narrowly missed Mr. Bush as Prime Minister Maliki stuck a hand in front of the president’s face to help shield him. - The New York Times

From Wikipedia:

In the Arab world: a gesture of contempt

In the Arab world, shoe flinging is a gesture of extreme disrespect. A notable occurrence of this gesture happened in Baghdad, Iraq in 2003. When U.S. forces pulled down a giant statue of Saddam Hussein during the 2003 invasion of Iraq, many Iraqi detractors of Hussein threw their shoes at the fallen statue.
This may be an ancient gesture from the Middle East; Psalms 60:10, speaking of some of the traditional enemies of Judah, says that "Moab is my washpot; over Edom will I cast out my shoe...." (KJV)
The shoe represents the lowest part of the body (the foot) and displaying or throwing a shoe at someone or something in Arab cultures denotes that the person or thing is "beneath them." Showing the bottom of one's feet or shoes (for example, putting one's feet up on a table or desk) in Arab cultures is considered an extreme insult. Examples include Iraqi citizens smacking torn-down posters of Saddam Hussein with their shoes, and the depiction of President of the United States George H. W. Bush on a tile mosaic of the floor of the Al-Rashid Hotel's lobby, forcing all visitors entering the hotel to walk on Bush's face to enter the hotel.
During President George W. Bush's surprise visit to Iraq in December 2008, an Iraqi reporter threw shoes at him during a press conference with Iraqi Prime Minister Nouri Kamel al-Maliki.

It is also what you scrape dogshit off of.