The Pokémon you though would never be in your team...

[ジャスミン]

Venomoth in Fire Red. I was surprised at how good it was and it helped tons against the E4.

 

[Pokémon Trainer Dylan]

I never thought that I would ever use a Nidoran. However, I almost always have a Nidoking/Nidoqueen on my Kanto team now.

 

[モモ果汁]

Never thought I'd use Porygon,but now I use almost everytime.Challenges are the exception

 

[Masterge77]

When I got Pokemon Black and White, I promised myself that I would never use a Watchog, I ended up using one in Black, she is still on my team as of this post.....

 

[Palkia]

I never thought I would Magcargo or Aggron in a in-game team. Both of them were personal favorables in my Emerald and Heartgold runs.

 

[Lashh]

There sure are quite a few Pokemon I thought I'd never put into my teams rotation.

Scyther is a for sure. I always wanted one, but they were so hard to catch, until I just caught him one day, first Safari Ball.
Victreebel on my most recent LG team- I've only ever raised one before, and I never thought I'd raise one again, but I decided to.
Dodrio is another, raising one right now in FireRed.
The Geodude line is one I certainly never expected to raise, but they sure can do some damage.
Pelipper, Roselia, Exploud, Altaria, Aggron, Ludicolo, Delcatty, quite a few from Generation III that I ended up raising when I initially had no interest in raising them.

There's so many more Pokemon I thought I wouldn't raise in my 10+ years of playing the games, but so hard to remember all of them, haha. A few I have yet to raise are Muk, Weezing, Jynx and Pinser, but I'll get around to it eventually.

 

[Sul_Zala]

Butterfree and Sandslash from a FR-playthrough. I had been away from Pokemon for some time and only recently restarted with Diamond and I never got around to actually beat Lt. Surge on my Red version, so I didn't really have any idea how to build up my team, so I went with what I got. And those two maimed quite a bit of the other trainers :D
From SoulSilver, I guess I'd never thought I'd have a Vulpix in my team. Granted, she's a Ninetales now, and it took me a bit to get one that hadn't forgotten Ember already, but she's so much more awesome than Rapidash.
BW: Larvesta/not-yet-Volcarona. I revamped my team before the E4 and currently training some Pokemons I left behind in favour of others, but she's back on the team.

 

[rippedupmemories]

I gotta say Furret and Bayleef, lol. I say a few walkthroughs, SuperSkarmory (person on youtube♥ he's an awesome....walkthrougher?) I saw his Furret and said "Why the heck would he use that?" I cought a sentret and....fell in love with it. Bayleef? Randomly chose a starter, and again, fell in love with it. I usally hated Chikorita!!

 

[Perriechu]

I always wanted Dragonite in the Kanto games and Salamence in the Hoenn games, but I couldn't get them in because they were so damn hard to train, Flygon and Gyarados are just as good right?

 

[Know-Nothing Bozo the Non-Wonder Dog]

I never used to like Pidgey, but I decided to use it when I restarted Red recently just cause I thought Pidgeot looked cool. Turns out it's actually pretty awesome. :) And soooo helpful when battling Erica, cause I didn't have a fire type.

 

[Ciax]

One of the weirdest pokemon in my opinion was parasect.
I thought it was so stupid. Then just recently i did a bug mono type run on fire red and spore + body slam is a deasdly xcombo and shroom was my mvp of that challenge.
Also lopunny, needed a 6th member so i used it in my diamond, never looked back