I did the ring before. That was not a good idea for me! I gained weight back and it was depressing to have to take the ring off.
hair cut, dry, style etc.
a day of shopping for you only (clothes, shoes, purse, whatever)
buy a new exercise tape or equipment... i love that!
get a new exercise outfit.
You really need it to be something like Susan said too... something that will help keep you motivated and moving... getting stuff to keep exercising is an awesome idea! I do that... and find that to be perfect.. but you still need other rewards too. I personally like the manicures and new leather purses lol.