Finger gun

The finger gun is a hand gesture in which the subject uses their hand to mimic a handgun, raising their thumb above their fist to act as a hammer, and one or two fingers extended perpendicular to it acting as a barrel. The middle finger can also act as the trigger finger.

It is also sometimes used by placing the "gun" to the side of one's own head or under the chin, as if committing suicide, to indicate a strong desire to be put out of one's misery, either from boredom or exasperation, or to express one's dislike for a situation. In addition, it can also be used as a way to say "hey" or "what's up" to friends or acquaintances. It can be used as an insulting gesture, as to suggest your brains should be blown out.

Sometimes, often with both hands, finger guns are used in situations where a person has intentionally done something cringe-worthy, causing second-hand embarrassment for those around them. (esp. a bad pun) The gesture claims ownership over the action and the intent, and can intensify the feelings of shame.

Children, teenagers and a teacher's assistant have occasionally been punished or removed from school for making the gesture. In some cases this was because authority figures interpreted it as a signal for threatening real violence, while in others they interpreted it as unacceptably supportive of gun violence in general. These have often been labeled "ridiculous" by some commentators.

In 2006, Fahim Ahmad allegedly made the gesture when speaking about the possibility of Canadian Security Intelligence Service agents ever coming to his apartment, which was used as evidence of his conspiracy to commit terrorism by a police informant.

Fans of Texas Tech University use a form of this hand gesture with fingers always pointed upward, called "Guns Up." The idea is that the Red Raiders, as the university's sports teams are called, will shoot down their opponents. The Guns Up sign is the widely recognized greeting of one Red Raider to another. It is also the sign of victory displayed by the crowd at every athletic event. In 2014 the gesture and cheer were adopted and adapted by the Southeastern Louisiana University Lions where the gesture represents an "L" for and the cheer is "Lion Up!"

...
Wikipedia