From when we first met Charlie, 'Walking on Sunshine' I knew she was going to be a very special character.  Like most of the people the Supernatural Universe brings us, she has many facets to her character, but her sense of fun, adventure and loyalty are what really stand out.  Highlights of her time for me are the whole flirting with the Security Guard while being coached by Dean 'Stop talking Charlie' and the Queen of Moondoor getting it on with a fairy!  Gotta love Charlie!