Haxorus - has a cool design, amazing Attack, a great Shiny form (unlike many other Dragon-types) and has Mold Breaker to destroy annoying Pokemon with Sturdy.
Sigilyph - found it a bit creepy at first, but it has grown on me. Magic Guard is an incredible Ability, and it has a wide movepool.
Cinccino - adorable, fast and can hit hard thanks to Skill Link.
Zoroark - Illusion is a fun Ability, and it is fast and has high attacking stats.
Reshiram - majestic and elegant despite its very simple colour scheme.
Other Generation V Pokemon I really like are: Samurott, Serperior, Stoutland, Krookodile, Mienshao, Braviary, Golurk, Chandelure, Archeops, Galvantula, Volcarona, Victini, and Terrakion.