If there was any pokemon I wouldn't want to have in real life, it'll probably be koffing 'cause It stores several kinds of toxic gases in it's body. And the fact that it could explode without warning alone is enough of reason for me. Not exactly the kind of pokemon a trainer would enjoy having.

I'd say Ditto. Ditto can take the form of anything and create an exact replica (unless it's going off of memory where it may get some details wrong). Also some Ditto's are unable to change their face but many are.

Existence of Dittos would be a scary thing as they could transform into important figures and commit heinous acts. They could also be used to transform into innocent people and then go on to commit crimes for their master and then have it pinned on the innocent people. Then there's also the chance that if either of the previously mentioned acts are committed then people could commit crimes or the like and blame it on a Ditto or something. Of course, there'll be many times people will be able to prove themselves innocent or that it was a Ditto with evidence but the overall impact would be constant public skepticism, and for those cases where it could go either way it may end badly for the wrongly accused party. Regardless of how many people are found innocent there would be many who were wrongly accused and never see the light of justice. 

This discord could not only impact court cases and people's profiles, but major political stuff and whatnot (especially if used by countries governments and government information agencies, etc.). It could cause tensions and skepticism to arise between many nations. Let's just say depending on how Dittos are used and in whose hands they could very well be the effective tools of the instigators of war, or the manipulators striving for corrupt power/control.

I'd have to say Psyduck. One, because if it sounds anything like it does in the anime, I would probably go insane from it whining from headaches. And Two, when they get headaches they do all kinds of crazy and unwanted stuff with their telekinesis which would be even more of a headache on my part.
DEATH  TO  PSYDUCK!!!

Hah, I'm not worried about the toxic gases, I'm to use that. I have a little brother. I'd have to say that I would absolutely not want Jigglypuff. No face paintings for me.

Snorlax. I could see him falling on something... like my house.

I wouldn't want to have Banette. Because the last thing I want is a possessed puppet that has a lust for revenge against the child who abandoned it. And I think that would apply to me if I ever stopped using him in my party, or left him for too long in Pokémon Purgatory (The PC).

Final Weapon : Maybe Honedge.  The Pokedex descriptions of it are as follows:

X: "Apparently this Pokémon is born when a departed spirit inhabits a sword. It attaches itself to people and drinks their life force."
Y: "If anyone dares to grab its hilt, it wraps a blue cloth around that person's arm and drains that person's life energy completely."

On second thought, I could use it against my enemies...MWHAHAHAHAHAHAHAHA!!!!

zero97axl : True.  But Ditto doesn't always make perfect copies...

supernerd117 : Oh yea, I remember that flaw about ditto. I recall playing pokemon mystery dungeon sky one time before and it's face still looked just like that after the transformation unto a blossom. I'm surprised that team charm didn't even noticed. XD

I would want an Eevee in real life, they are just so cute and it would be so awesome to have one around that would be like having a little dog. I wouldn't eeveen evolve it, I would keep it as an eevee forever.

I would not want a Gible. I would not want my head being bitten every 10 seconds by a 2 foot dragon Pokémon. 

zanderlex : The thread is about what Pokémon you wouldn't want, not what Pokémon you do want. 

RDay13 : Yeah, as soon as I got this notification I realized I read the title wrong.

I would not like to have a Jigglypuff as a Pokemon. Sure, it can put me to sleep instantly when I want to fall asleep at anytime. However, I don't want stuff drawn all over my face whenever I wake up...

One Pokemon I would never want to have in real life is Muk. It's pretty self explanatory just by looking at some of it's pokedex entries. Who would want a pokemon who "has a nose-bleedingly awful stench", and has a toxic fluid that "instantly kills plants and trees on contact"? Not me, that's for sure.

I was going to post what gamer said and will still do, muk is the first thing that came to mind he is someone I wouldn't want to have I mean your friends would even stay away from you. Because of how he stinks and all....he kills things with his odor... =_=

I agree with everyone on some Pokémon but my least favorite would have to be pikachu evolutions or Yveltal next to charizard.
I have so many electronic that pikachu might fry in a single bolt of thunder. 
Yveltal could turn me, my friends, my family, and everyone else into stone. 
Charizard would catch things on fire with its tail on purpose or accident

A Pokemon I wouldn't want to have in real life is castform because I don't think I want my summers to be rainy and my winters to be sunny. Even worse imagine the weather always changing because people won't stop using rainy day and sunny day that would be very annoying.

I wouldn't want to have an Electrode in real life because it would explode to entertain itself. That wouldn't be very fun.

Muk and Garbodor, they would probably give off a horrible stench. They would likely also end up dirtying any place they've been in. Overall a Pokemon that would create a lot of problems most likely just by standing in place.

Totally i would not like to be near a Magcargo, it is literally made of lava and i think i wouldn't last a day with one.