There’s the “fig” gesture where you make a fist with your thumb poking out between the first and index fingers. Wiki observes:
The general article may be of interest to the OP:
It also mentions the gesture where you raise your fist emphatically with a bent arm, and your other hand placed on your bicep behind the elbow - they call it the “bent elbow”.
Thanks yabob, but I had to bookmark the link. The way things are going in this thread, I may know all the gestures before the Body Talk book that **CalMeacham **recommended arrives. 
Same here. Actually, I had assumed this “there’s something wrong in your head” sign was universal in western countries.
From my American perspective, I suppose tapping the forehead could be taken that way, but it could also be used to say something like “Clever thinking! This here’s a smart one…”
Is this (tapping with the left hand your inner right elbow and raising your right forearm in the same movement, generally with the palm open rather than with the fist closed as shown on the picture) generally understood as “go fuck yourself” in most countries?
Weirdly enough, it’s called “arm of honour” in French.
There’s the Italian gesture of flicking the thumb forward from behind the top front teeth. I don’t know exactly what it means, but I know it’s the equivalent of “fighting words”.
This would mean “I don’t believe a word of what you said” / “That’s bullshit” in France.
Isn’t that the same or similar gesture Shakspeare uses? What it means exactly I do not know.
Is that like the “got your nose!” gesture? In Japan, that’s not used as an insult, but it is rude (supposedly it’s meant to indicate the female genitalia). We’ve had to warn my parents not to do it with our son, just in case he repeats it in front of the other kids and their mothers.
Putting your finger under your eye and pulling downward has some different meanings. In France, it means “you’re lying” or “bull” (ETA: clairobscur beat me to it). In Japan, it used as a children’s taunt (kind of like “nyah!”) and is usually accompanied by sticking out your tongue.
No, that’s biting the thumb. This isn’t a bite but a flick.
In France, it means “absolutely nothing” , in a pissed off or despising way. For instance : “You know how much this fucker paid me for my work?” : make gesture
Or “Upon my death, he will inherit that” : make gesture.
Don’t know if it has the same meaning in Italy.
Hijack : By the way, I’ve been wondering for some time what “ETA” meant. Or rather, I understand what it refers to, but I can’t figure out what the acronym stands for.
“Edited To Add”
I don’t see it that often, but around here it’s usually with the palm closed, often with the middle finger extended for good measure.
Overkill 
Make the Vulcan salute in front of your mouth, then wiggle your tongue between your two middle fingers. I have no idea what it means, but it looks deliciously vulgar.
It is rude in the same way that would be rude in a business meeting to put your feet on the desk (as a lawyer once did during my first and last consultation with him). It’s rude but it’s generally not used as deliberate insult.
A gesture considered as obscene as “the finger” in Italy is the cuckold, or “your wife fucks around.”
It is the same as the “hook 'em horns” gesture from the University of Texas (link to Wikipedia has photos).
Opportunities for misunderstood enthusiasm for one’s alma mater abroad abound. 
I have a theory about biting thumbs in Shakespeare. I wonder if perhaps they make “the fig” or some variant and then bite their thumbs so that they are biting genitalia (perhaps intended to represent that of the person being insulted; i.e. implying they are less than a man).
This is just a theory, I have no corroborating evidence.
It is, but I was informed by the Consulate when I was posted there that to Germans it’s much more offensive.
