Gold is a noble metal with and old tradition in jewelry. It looks nice and stylish. The only problem with gold is that it is quite a soft etal and therefore it is not recommended for initial piercings (although the EU standards allow it). The thing is that on gold microscopic scratches can easily appear. They irritate the skin and might provoke an unpleasant reaction. Also, because it is so soft, gold is not very good to use in tongue piercings, as chewing on might break it and even cause problems with taking it off.