The Ab Polonaise, The Rhapsody In Blue and Maple Leaf Rag I suppose. They gave me a kick to play when I was a kid fifty years ago and they always give me a kick now.
But they're just the longest standing examples. In a certain sense, Wolfi is right, every piece I play is in this category, including my own stuff. I have been in the habit of cycling through everything for years now which, given the relatively small size of my repertoire, isn't particularly hard to do. Of course this is easy for me to say because I am an amateur and I have never had to play anything I didn't really like anyway.