I have a cool new smily from Camille of a cool manga expression that is apparently referred to as The Sweatdrop
now how to explain this to someone who doesnt know the expression??
After a light search I stumbled upon this cool DevArt pic; though the few words cant really capture the richness of the expression..
Drawing Expressions pg 1 by ~Sai-Manga-Tuts on deviantART
Its a GREAT overview of the various options 🙂
A google search easily yields more examples
Anyway, it a very nice expression!