If this hasn't been said before, then I would give the nickname Vanoss / VanossGaming to my Rowlet. This is mainly because Rowlet looks like Vanoss' Owl Mask from his GTA V/GMod videos.
This is a tough call for me. Mainly because there are quite a small few Shiny Pokemon I don't necessarily like. Personally, I am in love with Suicune's shiny variation. It just looks so elegant... As for a Shiny Pokemon I would change... It would have to be Mega Gallade. And I would make it...
There's not a whole lot of Pokemon that I particularly hate, per-say, but there is one. And that one Pokemon is Gothorita. It just comes off as creepy to me, which I should be saying about Gothitelle, but for some reason I like Gothitelle more. Is that weird by any chance?