Rarest and hardest to get pokemon?

[Cyphre]

The title basically says it all, i was doing a Dragon Monorun, but i would like to make a team from the rarest and hardest to get Pokemon, just in case. 

So, obviously, Poipole/Naganadel is the hardest one, cause completing the dex is a massive time sink, requires a huge patience, googling and community help. So that is one. 
I feel like Mimikyu is also pretty obscure, running around like a moron in the desert for 4 hours is torture enough, and after finding the Mirage Tower it's easy to complete everything, get your Aegislash and forget about it, so i feel like comparatively not many people will even find the basement. So this is the second one. 
Maybe you can make a case for a Spiritomb, since Odd Keystone got absolutely nonexistent chance of appearing during the mining, although it will be buffed to 1% in the final version. 

What other pokemon are currently the hardest to obtain, rarest and most obscure currently? 

[logintomylife]

For me it was Torchic, if you don't get hints from people that already did it and figured it out, it's really hard to join the fact that the basement in Agate city has a pattern on the ground that unlocks secret room in Charlotte's gym xD

 

Otherwise I do agree with ya on the others, and I would add Beldum with the Tauros glitch, which is splendidly done, and you wouldn't figure it out if someone haven't done it already 

[Seel The Deal]

Beldum - You need to slot a Data Chip in the Wasteland Hideout healing station (AFTER city restoration, too, which means you have to return to the area, which is otherwise seemingly unchanged), white out or use Teleport while riding a Tauros, and bring it to the previously inaccessible cave along the secret passage to Squirtle. You then have 9 turns to catch a Pokemon with a catch rate of 3, barring Sleep, Paralysis, Ghost-types etc.

 

EDIT: Ninja'd

 

EDIT 2: Zangoose, pre-restoration. You have to find it at four different locations during specific weather and time which all unlock at different points in the story. You're not unlikely to learn of its existence, but to actually encounter it you basically have to google how to find it.

[Cyphre]

Well, i agree with Torchic overall, but he's got all this starter thing going on, so there is that. 

Yeah, Beldoom and his line is a fair contender, absolutely. 

Lapras that appears only on friday in a very specific diving spot is kinda obscure too. 

[Anjuna]

Apart from the ones mentioned in this thread, I'd say gible.

1. Journey out into the desert, which is hellish to begin with
2. Make your way through a quicksand dungeon where the only way to learn how to get through is by tedious trial and error
3. Activate the two switches and backtrack
4. Somehow make your way through the garchomp temple (Which is a goddamn nightmare!!)
5. The simple act of ENCOUNTERING the pokemon itself is via an RNG-based puzzle

Luckily, I got a 2IV breedject on WT, so I didn't have to go through all this 

[Moto]

Phione is up there. You have to complete almost the entire mirage tower, which is hard enough to begin with, then it is a 1% encounter by fishing in the tiny "fake" desert area you get put in right before completing it. 

[kithas]

I think Beldum for the bug-ish method and torchic for the same, being the same with Mimikyu mainly because you don't get any hints of those methods. Gible isn't so difficult imo because you can have Taka with yourself who kind of helps you or hints it, Spiritomb is also doable given you got the Odd Keystone you know what is it for. Poipole isn't as difficult as time-consuming since there is a clear good prize to the sidequest and you could (in theory) be traded all the items needed.