Pikachu.

This shouldn't come as a surprise, but I freakin' love this little guy. The star and basically face of the series, Pikachu. This electric mouse isn't afraid to give is a trainer in the anime, Ash (or Satoshi in Japan) a little zap every now and again. However, not everyone knows that Pikachu wasn't originally going to be Ash's Pokémon, it was going to be Clefairy. The show really brings out the sassy personality of Pikachu.

Eevee

Also not a surprise, Eevee! This Pokémon has eight evolution forms for each different type, and each one is as cute as the next. I feel like you can't really go wrong with having Eevee in your party.

Piplup

Honestly out of all of the starter Pokémon, I think my favorite would be Piplup. I've played "Dimond/Pearl" games many times and I've played with the other starters from those games, but I keep going back to Piplup. This little one is fun, strong, and is very passionate, even after evolving to Prinplup and Empoleon.

Lucario

I've liked Lucario since the movie "Lucario and the Mystery of Mew," as well as "X" and "Y" when Mega Lucario was introduced. You could first get Lucario in "Dimond" and "Pearl" by getting a Riolu egg and evolving it. You can never go wrong with having a strong Pokémon in your party, who also has a lot of heart.

Gengar

Gengar can sometimes be perceived as the bad guy, like in "Mystery Dungeons." But there's some lore behind him, about being Clefable's shadow. They're both immune to each other, ghost and normal types of some immunities towards each other. Also, Clefable is the evolved form of Clefairy, who if you remember from Pikachu, was almost Ash's first Pokémon.