The :sax: is the unoffical mascot of Animated Diversions Forums, and originated from this music video of "Get a Move On" by Mr. Scruff. The term 'sax' is generally applied to the people-blobs featured in the video, specifically the spinoffs originating from ADF, such as :monosax: and :angrysax:. The rest of the 'original band' are referred to as :guitar:, :trumpet: and :drum".
The orginal :sax: started out as a emoticon from Something Awful Forums before being adopted by ADF. Currently it resides in the "Stupid Shit we can't wait to delete" catagory, but has remained there for many years, along side the 'original band'.
Proper usage of :sax: is debatable, but is generally used as a sign of positivity or approval in posts by most users. Use of :guitar:, :trumpet:, or :drum: can be substituted for :sax: in most situations.