Riamus
Hunter
Although possible to make a wheel shape right now, you can't really make a paddle wheel such as you'd see on a watermill or a steamboat. Although limited in scope for where they'd be useful, they would allow for some POI that we currently can't make look all that great right now. I know this is probably something that will end up needing a custom block set from a mod instead of vanilla because of the limited scope of usefulness, but I really think they could be a great addition in vanilla as well.