Dusknoir, Jellicent, and Chandelure
I used a Dusknoir for the first time in my playthrough of Alpha Sapphire last year, and even though I wasn't a fan of its stats, I was glad I finally got to use a Pokémon who I have always wanted to use since I really like its design. thanks Arc for helping me evolve ;P
Jellicent's giant moustache thing is captivating, but I'm not too fond of the female form. Its combination of Water and Ghost is interesting and I like its creepy Pokédex entry about sinking and vanishing ships.
Chandelure is another Pokémon with an interesting type combination. I believe I used one when I first played White years ago, and I enjoyed using it.