This is a difficult choice since there is a lot of good Pokémon out there. I will probably go with a Pokémon that I am quite fond with.
I would have to choose Persian as my first Pokémon because it has been my favorite since I first found out that it existed. My second choice would be Snorlax due to its Thick Fat ability and being able to learn a wide variety of moves including Surf, Fire Blast, and Thunderbolt.
Porygon-Z makes an awesome normal-type Pokémon as well. With some choice specs, it gets sky-high special attack, and the fact that it can learn Ice Beam, Thunder and Psychic as well as Tri-Attack is a great bonus. It's definitely a Pokémon worth using at some point.