This is going to be sort of a long shot but, I wouldn't want to be Smeargle or Ditto. The best part about life is being yuorself and defining yourself through who you are and what you do.  Smeargle and Ditto can essentially only copy what others do and in ditto's case appearance. I would hate that. I would lose all creativity and individuality that I have and that is the reason that I wouldn't like it. I wouldn't be me.

I'd hope I wouldn't be a Magikarp as I'd be as useless as decaffinated coffee.
But it would be cool if I'd find a hidden stash of about 19 Rare Candies by the water and use them all and evolve straight away to Gyarados though.
But I'd still hope I wouldn't be a Magikarp no matter what.

Well, I could go for the typical response, but naw.

I would hate being a Suduwoodo. Reason is, the Suduwoodo can't move. I want to be able to move freely, not be stuck in the ground! Also, I don't want to be fought just because I'm in the way. At least as a Bonsely I could still move.

Snoralax. I cannot stand the thought of being that lazy. I mean come on? Who would be able to stand it?

I'd honestly enjoy most of the Pokémon despite there flaws. I would especially enjoy some of those that people put they wouldn't want to be. Eevee for the fact that I could show people I could be whatever I wanted no matter what they told me. Muk because if I was caught by a trainer I would love them forever. And as a muk I could live in my own stink. Zubat would be great to be because if I worked hard I could learn amazing attacks, I'm adorable, and plus I love sucking enemies life away and making them hit themselves, but before I carry to off topic. What Pokémon would I not want to be?

... Spoink. Although there is a lot of Pokémon I don't like for there design, power, or just general uselessness in all categories, Spoink is not one of the Pokémon I hate. In fact, I love this Pokémon for how cute it is. It cutely bounces on it's spring, it's simplified, and it's just a cute little piggy. It's evolutions may not be the best, but that's not why I wouldn't want to be this Pokémon.

Spoink's PokeDex entry! I'll quote it for you
   - "Spoink bounces around on its tail. The shock of its bouncing makes its heart pump. As a result, this Pokémon cannot afford to stop bouncing - if it stops, its heart will stop." -Ruby Pokedex Entry | source: Bulbapedia

I can't handle exercise enough, but having to jump for your life and never stop. What if you fall over from battle! That's murder! And what about in the pokeball? Do I still have to jump or is there a magical mini nurse joy in there to help me... it's a little ridiculous.... the poor thing.

DestinyHeroDC : Well if you were a Snorlax, you would have lots of power and you wouldn't have to worry about a lot since you'd be sleeping all day. It's a lot better than being a Luvidsc.

FaithFighter : You spelled Metapod right but you spelled Kakuna wrong. It wouldn't be all that bad to be either, though. I mean Butterfree and Beedrill are two of the coolest bug types. Evolution would probably follow the Anime rules so you wouldn't have to go through the trouble of leveling up. I mean literally, it takes forever to level them up if you try to face wild pokemon to do so. It is a pain, I swear. Butterfree is worth it early, but it takes a few levels for Beedrill to be worth it.

The Pokémon that I would not want to be are Magikarp, Goldeen, Metapod, Kakuna, or Porygon. All of these Pokémon got the short end of the straw when it comes to strength, usability, and appearance. I would rather be a more useful Pokémon like Blaziken, Golem, or Alakazam to name a few. I always hated when I had to play with the first four that I said I would not want to be because it was extremely difficult to level them up. The fastest and easiest way to get Pokémon similar to these to level up is to use EXP. Share. That way you can use a more powerful Pokémon, you know that can actually attack, to defeat the enemy. This item is my favorite, and I am glad that it has made it in the games at least up to Sapphire and Ruby. Anyways those are the ones I would/wouldn't want to be with a little extra.

The two Pokémon I would never want to be are Lopunny and Gardevoir.And I can tell you why with just one word which is "Internet".
It would destroy me,especially since I would be a male one. 

im gonna say Gulpin whos gonna want you as there pokemon 

Hmm, decisions, decisions. So many stupid Pokémon to choose from... hmm, I think, in all honesty, I don't want to be that irritating Mr. Mime. No clue why, but he irritates me like no tomorrow.

So many pokemon I wouldn't want to be, if I'm honest.
Dunsparce is a definite one. If you ever get caught you just rot in the PC because no one will use you.
Wobbuffet would suck, since you spend so much of your life getting hit.
Ditto would also suck, since you can only really transform and rot in the daycare.

There are a lot of horrible choices to be. Ditto sure, because of daycare. But what would really be the worst is Cubone. I mean, it spends it's whole life mourning it's mother, and wears her skull...On it's head...Yeah.

ShinyInfernape100 : To be fair, Garvevior can create black holes. So if it came down to that you can use your quantum physics to dematerialize people. If that isn't fun I don't know what is.

Gastly, the worst Pokémon of them all in my opinion (for Ghost Types), Magikarp is really good with his advantages though, totally! Kidding, but it'd be nice to not be Gastly OR Magikarp and maybe we'd all feel free of wretched Pokémon like them.