[drhodes]

An icon? no. There are however, online hanzi dictionaries where the user draws a character, here's one:

http://ce.linedict.com/dict.html#/cnen/home

See the paintbrush next to the magnifying glass in the search field.

[yorwba]

Also not for icons but for math symbols: http://detexify.kirelabs.org/classify.html

Really useful when you want to use "that squiggly thingy" but don't know the TeX command.

[dTal]

I usually jump straight to http://shapecatcher.com/ for arbitrary Unicode.