Otherwise there's the hand in front of the face to say you've lost the plot (as mentioned earlier) or you're nuts, but that is only Swiss German. The Swiss French do not use that gesture.
Index beneath the chin, slip fowards once or twice with an indifferent expression to say: I could not care less
The first time I saw that gesture was in the mid 'sixties. Palm towards your face, fingers spread and roughly horizontal, and you had to wave the hand up and down. The result was a flickering effect in your eyes, like on those old TV set.
The meaning was, "You're brain-damaged because you watch too much TV." Now I wonder if that was just a temporary and / or local phenomenon or if that possibly was the way that gesture came into being.
I don't know the real origin but I remember using it as a kid in the States (mid-70s). At first, the proper technique was to bend the index and ring finger at the first bend and protrude them out from the middle finger. This looked like a pair of balls and a penis to really say, " You!". After a couple of years, the cool kids started to fold all the fingers into the palm and just stick up the middle finger. The meaning stayed the same. The kids that didn't catch on to the new technique were ridiculed until everybody switched. I'll still throw an old-skool bird once in awhile for nostalgic purposes.
I have also heard this story as the origin of the V sign. In the absence of anything better, I am inclined to go along with it.
Of course, this is with the outside of the hand towards the other person. The other way round is the Victory sign as made famous by Churchill during WW2.
It's not a hand gesture but it's something that is quite infectious and I have noticed that I have subconsciously started to copy it in my years here.
It's where people faintly jut their chin and point it in the direction of whatever or whomever it is that they are talking about mid conversation. It's really quite subtle but after I noticed it once or twice I saw everyone doing it.
I guess everyone remembers this "proposed replacement" for the Twin Towers -- with a nod to the "old school", I learn from the above ...
My husband (Swiss) does that all the time. It means "I've got my eye on you", but usually it is meant tongue-in-cheek, not harshly. For example if I make a smart a** remark, he will make that gesture.