There are some other Etter-bred crabs that are less well-known than Wickson but worth trying, such as Crimson Gold, Vixen, Muscat de Venus, Atalanta’s Gold, and Amberoso. All but Crimson Gold are difficult to find except as benchgrafts from Greenmantle Nursery, as they’re trademarked and require non-propagation agreements.
Some other small-to-crab-sized apples that are also worth trying: Chestnut, Trailman, Kerry Pippin, Margil, Wyken Pippin, Yellow Ingestrie, and the aforementioned Pitmaston Pineapple.
I’m growing all of these as either trees or grafts, but so far only a few are old enough to bear yet. (Actually, Yellow Ingestrie has eluded me thus far, but @derekamills will hopefully be able to remedy that next season.)