I like Orthworm a lot, I was pretty enthralled by this steel worm Pokémon. It's pretty cute and the hands on its steel core is interesting. It's the first one I think from the new generation I really liked, similar to Appletun from Generation VIII. I have one on my team for Pokémon Scarlet even.
They definitely peaked a little when making Steelix. Although I've always had a soft spot for Aggron.