Dewgong. At one point during my elementary school days, I remember Dewgong being prolific for knowing Sheer Cold. I believe there was a certain one floating around the little network of trades we had going on. I forgot if I ever owned it myself, but I'm pretty sure I had battled it at one point. And boy, it was something to fear.
Lapras. It's just super adorable, and I really liked how you obtain one in XY. I honestly didn't feel like using any Pokémon I had that could help me surf across the Kalosian waters, and most of them were very weak at the time, so that was really helpful.
Articuno, one of my favorite Legendaries (this applies to all of the Gen 1 legendary birbs). All three of the birds are also among my favorites, but I can't pick a favorite amongst that three. They all look awesome, but in their own way. Zapdos' design is extremely
cool (no ironic pun intended), while Articuno's exceeds in pure
beauty. I'm trying to figure out a word to describe Moltres, and no, I'm not attempting to keep a theme of Contest type names.
Sneasel/Weavile. After seeing the
Pokkén reveal trailer for the latter, it instantly became one of my favorite Pokémon. <3 They gave her so much personality in that game.
Regice. I just like the Regis' designs in general.
Glaceon. I absolutely
adore all the Eeveelutions, but Glaceon is undoubtedly one of the most adorable ones. <3 Leafeon may be my 2nd favorite Pokémon, favorite "-eon" and favorite Gen IV "-eon" at that, but Glaceon's design strikes me with charm and adorableness that a handful other Pokémon can achieve for me. Along with Leafeon, I believe its design is among the best in Eeveelutions, as well.
Cryogonal, as one was on my team at the time of my first compilation of White version. And it's got a nice design, too.
Amaura, one of the most recent additions to my favorite Pokémon <3 I'm currently playing through Y the first time, and a couple weeks ago when I was at Glittering Cave, I looked up the two fossil Pokémon I could choose from. I had already seen Tyrunt around many times before, but I've rarely seen Amaura. At that moment, I also fell in love with its design that it was an easy pick for me. And now, I'm carrying my little guy with me all the way to the Pokémon League. I love him so much <3