If you could have one Pokemon, what would it be?

[The name master]

Self-explanatory.

Choose one Pokemon you'd use in battle

And/or:

One Pokemon you'd have as a pet.

I'd have an aggron as my battle Pokemon, and Zigzagoon as a pet.

[Reshiram54]

I'd have an Articuno for battle (and riding off into the sunset like a boss) and a Zigzagoon for a pet. They're just so cute! :3

[The name master]

Wow! Zigzagoon must be very popular as a pet! I chose Zgzagoon, you chose Zigzagoon, even in an animation I've made, the characters have a Zigzagoon (nicknamed bandit) as a pet.

[TheDesertPro]

Wow I guess I'm the odd one out my battle Pokemon would be Lulu (my Lopunny) and my pet would be Mightyena. Why Mightyena? Well I love wolfs and dogs a lot and technically my Lopunny would also be a pet same with reshiram54's articuno and your Aggron  so technically the question would be what Pokemon would you have as a pet and fighter.

[Skittyglameow]

If it were me, I would choose Mew, for both as my pet an my fighter. Why? Simple. There's too many I love! XD

[Kpyna]

I'd definitely have a houndoom for both! I'm hoping Pokemon Go will let me complete that dream :p

[Morgan Archer]

Swampert My Swampert took me through the first 6 gyms in Alpha Sapphire unassisted

And through almost all of the Team Aqua battles, his type combination is wonderful and he's a great sweeper

Also being able to Surf around on the big buff water dog is pretty useful

[Captain Jigglypuff]

Jigglypuff would be my pick of course. But I'd choose Sewaddle as my pet since it is my second favorite non-legendary. It'd be female and I would call her Sewsie.

[The Shrub Dragon]

gardevoir all day every day

[Flintzer0]

I'd have a Hitmonlee for battle, and a Swablu for a pet (in several Pokedex entries, Swablu is stated to enjoy landing on people's heads and pretending to be a hat, and therefore is supremely adorable).