>Hey Catdaddy!
>Does sign language count?
>
>Jay
Well of course...except the universal monodigital salute (bird). 
Actually, it really does help to know sign customs of other places. For instance...and these might be out of date:
In America we have a standard wave meaning goodbye, come see us again. In some countries almost the same gesture means roughly "Go away, I want nothing to do with you". The come see us again gesture is done with the palm toward you.
In a pub in England, turning a glass upside down used to mean you wanted another round. In Australia, it meant that you could "whup" any man at the bar. Of course, as mentioned, these can now be outdated, or perhaps they were regional. Some folks from those areas could verify whether they are still in effect.
I guess the point is that you need to know the local sign language before using it.
How's that for a semi-serious answer to a non-serious question 