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.
Oh boy. There some good ones, but I’ve got to go with Metagross. I had not seen it before and when I was playing Pokémon Colosseum (or XD?) the boss had one. Terrifying.