Zorua- it's really cute. I've always had a fondness for it ever since I saw it, along with Zoroark, released in the 4th gen.
Volcarona- I thought it was a Legendary at first. But, of course, I was mistaken. But when I found out it wasn't a Legendary, it made me like it more. Not only is its design badass, it also packs a powerful punch!
Gothitelle- I'll be honest here, and say that I didn't like Gothitelle at first. I thought of her to be a rip off of Gardevoir, one of my favorite Pokemon. But over time, I started to like Gothitelle more. She's actually not a bad Pokemon at all.
All the Ghost Types in this gen- I love Ghost Types.
Musharna- even though somewhat creepy, I love the cry and the inspiration of Musharna.
Oshawott- my favorite Starter out of the bunch.
I think this covers it.