Former president George W. Bush making the "pitchfork" gesture during a visit to the White House by the Arizona State track and field team.
The pitchfork is a hand gesture used predominantly at Arizona State University and events in which the school's athletic teams, the Arizona State Sun Devils, are taking part. The Arizona State mascot is Sparky the Sun Devil, who carries a pitchfork. The hand gesture is especially popular among Sun Devil fans at athletic events, such as football, in which cheering is a large part. The Houston Cougars use this hand symbol as well. The Houston Cougars have been using the hand gesture since 1968.  The hand gesture is also popular among professional wrestling fans.
On November 20, 1946, the mascot of Arizona State University was changed from the Bulldogs to the Sun Devils by the student council, after a November 8 vote of the student body for such a change. Two years later, a former Disney illustrator named Bert Anthony was the first to add an actual trident to the Sparky image. It is not known exactly how long afterwards the pitchfork hand gesture became popular, but there are references to the gesture being used as far back as the 1970s. According to the Arizona State Press, three students came up with the pitchfork hand gesture in 1986 
In a well-publicized image which was taken in late 2008, many websites and blogs mistakenly reported that George W. Bush was making the sexually connotative "Shocker" hand gesture when in reality he was making the pitchfork sign due to the visiting Arizona State men's and women's track team.