$ for sha is bad idea. This symbol is reserved for dollar.
I think its a little different. it is not $, but seems most of ppls think they are the same maybe.
(if we can use that, it will be the best one.)
anyone has the idea of a good symbol, all welcome. lets find it out.
another example:
http://i.imgur.com/JPUHdyK.png
http://i.imgur.com/oaN5Upg.png
This one is cool
