I love reading the answers to this question. This is a tough decision and I truly didn't think I could pick a favorite. Almost all of the Disney characters evoke some treasured memory for me. Then I remembered my most recent trip to WDW. I had left Wishes early and was in front of the train station waiting for my family. I had a wonderful view of Mickey waving and saying good night. There was a little guy, maybe 2-3 years old and when he spotted Mickey he absolutely lit up. He toddled to the wrought iron fence and he looked from Mickey, to his parents, to me, with unabashed glee. He knew, that Mickey was waving to him, just him. Several hundred other people knew he was waving to just them, also. Yeah, I teared right up and I felt privileged that the little guy had included me in that special moment. Looking back over a 50 year history with Mickey I realized that during all my encounters with him, be it in person or via TV, he has always made me and everyone else feel special.
I gotta go with Mickey.