Writing a fictional alien culture means more than just coming up with a language and customs. Real-world cultures oftentimes rely on nonverbal communication, so a realistic fictional culture should have its own instantly recognizable hand gestures–its own versions of thumbs up, flipped birds, or figs. Plenty of science fiction creators have realized this, and given their fans an array of iconic gestures to emulate at conventions.
Live Long and Prosper (Star Trek)
This is the hand gesture that’s so famous, even non-fans of Star Trek know it and the phrase that goes with it. The Vulcan salutation of an extended palm with thumb stuck out and fingers splayed between the middle and ring ones has been used as a Trekker shibboleth since the original series was still on television. This actually wasn’t even in the script originally, and, incredibly, one of the most iconic moments in all of sci-fi came from an on-the-spot improvisation by Leonard Nimoy. The devoutly Jewish Nimoy wanted Vulcans to have a more “logical” version of a handshake, and based the gesture on the ones Orthodox rabbis use when praying on the High Holy Days, which represents the Hebrew letter shin. The live long and prosper salute has a reputation for being difficult to perform without a certain degree of manual dexterity; one character in a Star Trek film even offers a handshake after being unable to do the Vulcan gesture.
Jedi Mind Trick wave (Star Wars)
There are many benefits to being a Jedi; it turns out the power of the Force has a lot of worldly applications for the ascetic monks who aren’t supposed to use it for gain. The best way to channel the Force for fun and profit has to be the famous Mind Trick. A subtle application of mental energy plus a calming, authoritative tone of voice lets the enterprising Jedi convince weaker-willed individuals of just about anything, like Obi-Wan telling the Stormtroopers that Artoo and Threepio in fact weren’t the droids they were looking for. The key to all of this may be the hypnotic qualities of the hand gesture that accompanies the whole rigmarole–a simple open-palmed wave in front of the face. Move along!
Universal greeting (Transformers)
When the going gets tough, you’re backed into a corner, and you’re at last in a situation you can’t talk your way out of… why not try the universal greeting? The phrase “bah-weep-graaaaagnah weep ni ni bong” is understood across an inconceivable number of cultures and galaxies to mean either “we mean you no harm,” “care to dance,” or “do you hate the dirtwad Decepticons as much as we do?” as appropriate. The greeting, first seen used to pacify hostile Quintesson drones in the 1986 Transformers animated feature, is best used alongside a friendly gift, and of course has a kind of secret handshake associated with it: The Transformers wiki spends a whole paragraph describing how to pull it off correctly, although it essentially amounts to a glorified game of pat-a-cake.
Giga Drill finger (Tengen Toppa Gurren-Lagann)
The heroes of Tengen Toppa Gurren-Lagann are fueled in their quest to liberate humanity from extradimensional alien tyranny by heroic determination, fiery emotion, and drills. Realistically, mostly drills. Since protagonists Simon and Kamina were living underground at the beginning of the series, it’s only natural that they would base their weapons on earth-moving machines. We most often see drills used against the Beastmen and later the Anti-Spirals in the form of a Giga Drill Breaker–a kind of attack that manifests a huge drill made out of energy from the user’s upraised index finger. Besides a weapon of war, the finger pointed above the head becomes a symbol of hope and a representation of ascension for a people long oppressed.