Hmmmm....I like all my clients. The one I'd say is my favorite right now (only because the other client that's really my favorite is at a real job right now and not working in her business) is a woman I call 'classy'.
She always has good input, asks the right question, thinks I rock!
She know the value she gets for her dollar so there's never any pulling of teeth to get payment. She also sent me a referral to another great business woman I love working with.