I honestly thought Buizel would evolve, back in Sinnoh Ash really had a full powered team comparable to Kalos. I can forgive Gible because it joined the roster pretty late, but Buizel was been there pretty long, from Dawn and then to Ash, and he even showed some amazing battles. After look at Unova saga with how he easily evolve Pidove, Roggenrola and Sewaddle, I think Buizel deserves some justice!
On a side note, Snivy and Oshawott would be my next 2 pick. Snivy was already shown to be overpowered at the start, and she also seem to trust Ash anyway. I don't know if there is a dedicated episode that shows Snivy hatred of evolving, and I hope Trip's Serperior isn't the reason Snivy can't evolve, because back in Sinnoh both Ash and Paul had Torterra anyway. Ash's Oshawott... I don't really like him at the start for what he shows, but he was given decent character development (which is superb considering Ash had like 10 Pokemon to rotate in Unova) so I was hoping him to evolve into at least Dewott to impress me but it didn't happen at the end. Ehh... in the end found out that Oshawott is my most hated Ash's Pokemon but I would give him a chance to redeem himself should he evolves into a Dewott.