I use my initials as my signature, and since I recently acquired an additional last name with getting married and all, I now sign all receipts and most correspondence as "stg". All lowercase.
I love this simple initial stamp made by our favorite French stamp maker. Wouldn't it be fun to make homemade cards and stamp this on the back for a little personal touch? So sweet. Plus, he makes face stamps, origami mobiles and his Etsy shop motto is "stuff made in France with love and patience". How could you not shop from this guy?