It'd have to be Poipole and Nihilego. Poipole because it looks pretty cute and can evolve. Not to mention it's got a pretty cool type! Nihilego because I like the jellyfish vibe its got. It just looks so calm and smooth that I don't immediately feel put off by it. Many other of the UBs fall into the Pokemon uncanny valley for me, which I get that's the point, but I'm not a big fan of the other UBs. Doesn't mean that they shouldn't exist, they're just weird to me.