omastar is super cool. It's a cephalopod, creatures which I love, and unlike malamar and octillery it's neither somewhat awkward looking or overly plain. I love its sky blue body, its snakelike eyes, its four-unit beak, and the spikes on its shell. I'm also a fan of cradily, tyrantrum, and to a lesser degree archeops.
My choice is Lileep/Cradily. It's a Grass type, I love Grass type, Grass/Rock is great as a combo, it's a defensively solid Pokémon with a nice movepool and the mysteriousness from which is surrounded is just something I find utterly appealing.
Carracosta is awesome, I love its design and the story on how a Pokémon very similar for Tirtouga was considered for Gen II but it took it 3 gens to finally make it as a Pokémon. Armaldo is awesome too, but it's disappointingly horrible in battle.