Okay so here's what happens: a genie appears one morning in front of every person on earth and offers them a deal.
"You can choose ONE pokemon, and that pokemon will become your companion for life. It will live as long as you do, and stay attached to you until you die. You will be closer than you have ever been to any pet. This pokemon will be able to evolve but only if you want it to. It will be able to fight other pokémon, as in the games, but it is not an obligation: it can be very happy simply being a pet, to cuddle you, to accompany you, to comfort you. Evolution can happen even without fighting: pokemons often evolve depending on their happiness, their sense of accomplishment. Fighting is not the only way to achieve this. Moreover, it will obviously be able to use its special abilities, such as flying, super-intelligence or fire-breathing, to help you in your daily life.
But be careful: a pokémon needs attention. You will have to brush it (if it has hair), feed it, take care of its needs... Not all pokémon need the same level of attention: a big pokémon like Druddigon or Beartic eats much more than a Caterpie or a Luvdisc. This can cost you a lot of meat on a daily basis. Also, some pokémon are only happy in certain environments: Snorunt needs a very low temperature, while Alomomola can't live out of water. You'll also have to adapt to its needs.
Finally, you cannot choose a legendary or mythical pokémon. Ultra-beasts are allowed."

Do you accept this deal? If so, which pokémon do you choose? And why?