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

[Westie7]

Ariados, Crobat, and Tentacruel all showed me how awesome they are at various points, my Crobat in a Crystal run and several runs since, and Tentacruel and Ariados in my Poison Monotype challenge. Dabbling in competitive play has shown me that Quagsire is a boss, and I plan on migrating him over to Hoenn for the inevitable Gen III remake coming up, as well as an Extrasensory Cyndaquil. I may or may not make that a trio run with Claydol.

I also have new found respect for the Oddish line through Vileplume, because despite their poor Gen III moveset, he's proved invaluable in my Poison Monotype through Sapphire and my as-of-yet unfinished Nuzlocke challenge. I've basically discovered that Poison is amazing, despite being horribly under balanced.

 

[Charizard★]

Geodude for me, but it's really helpful when it comes to HMs and all, so it's nice to have around.

 

[Alternative]

I have to agree with Karpman on the Geodude thing. I was playing through Pokemon Red on a challenge, in which I was allowed to use Geodude, and I was struggling with Jigglypuff to get through Mt. Moon, and I pretty much instantly took on a Geodude and it beat everyone with Rock Throw. It was pretty good.

Also on my first run of Black I used a Sigilyph which I didn't think I'd use. I just caught it because it was rare. The same thing happened with Darmanitan. I got to Castelia City with two Pokemon and realised I needed another one. I found a Darumaka and then was like "yep, using it". :)

 

[Tyranee]

Altaria - Never thought much of this dragon/flying type until I used it on Black and found out it can be beast.
Magikarp - Part of my new Emerald team (I restarted). It's a pain in the butt to train but Gyrados is beast so it's worth it.
Mareep - Saw this said earlier. I didn't think I'd be using a stupid sheep but Ampharos has some great stats.

 

[CptSwaggerPants]

I firmly believe every Pokemon is strong if you care about it enough; that is why I try to coalesce every Pokemon into my team at some point. For example, I always use my Skuntank and Zoroark but I am now also training a Shuppet and an Aggron.

I also urged my boyfriend to use a type/Pokemon he's never used before since he is so fond of only bug types; he started using a Marowak and now it is one of his favorites.

 

[Almost Me]

My emerald team contains a couple of guy's I'd normally never use.

1. Pelipper. I mean seriously. Its stats are mediocre, but as a water-flying it has its advantages. Being both a surfer and a flier cuts down on useless party members, and it's one of 2 ways I have to stop fighting mons - the other is Gardevoir.

2. Cacturne. Late in my game, I realised I had no grass mons, and set out to catch one. I like Dark-types, so Cacnea seemed a reasonable choice. Skip to Cacturne, and it sweeps Tate and Liza.

 

[miltankRancher]

Toxicroak. Hahaha. I used to one hit croak's back then, but during my poison monotype, Toxicroak was a beast. Ice Punch, Thunder Punch, Revenge, and Stone Edge, it helped me stop Cynthia in her tracks. Talk about winning.

 

[razzbat]

in my most recent run in pokemon black i used a krookadile, which i never thought of using. he's pretty awesome though, as ground types usually turn out being.

 

[Eeveé]

on saphire i was doing a mono water run never would of used
pelipper before whilst weak as a wingull once it evolved it was one of my best with
shock wave, wing attack, surf, return
and ludicolo strength, surf, nature power, giga drain

 

[Hikamaru]

When I first played Ruby I was often thinking of strong, tough Pokemon.

When I caught Electrike, I thought it wouldn't give my team potential. Now, she's a hard-hitting Manectric at Lv100!

It was this moment why I have another Manectric in SoulSilver - to bring me back my memories of Ruby.

 

[Atomic Pirate]

Lanturn. In Emerald, I needed another party member, so I picked up a Chinchou. It turned out to be a good Pokemon when it evolved, so now it's one of my favorites.

 

[poopnate]

Pidgey.

On a Nuzlocke run of LG, I used a Pidgey as my Second in Command up until Mt. Moon where she died after surviving a Thundershock from both Voltorb AND Magnemite (stupid Super Nerd... D: ). She was a great pokemon and I never much used the Starter Birds (Pidgey, Hoothoot, Tailow, etc.), but I'm starting to like them now. :P

 

[King Of The Blues]

The most recent and probably the only Pokemon I recall of not imagining being on my team but ending up on my team would be Sandile. I didn't like it at first nor did I like it's evolutions but I knew it was a good Pokemon in terms of stats and in terms of it's move-pool so I had to have it and then eventually it grew on me and I started to like it's looks and just everything about it. It proved to be a Pokemon that played a vital part in my journey in Pokemon White as did the other Pokemon.

 

[Sandshrewiac]

Wobbuffet. I HATED it until I found a use for it's ability against Entei and Raikou on SoulSilver. Now It's a staple of my team.

 

[Lee Know]

lol, the Jellicent, Hydreigon, and Eelektross I have on my team now. I always thought Jellicent was rather silly, until I finally got a Frillish, and then it proved to be a way better choice than Swanna lmao. Originally, I had a Zoroark as my staple Dark type, but even though it was fast, and strong physically and specially, it was incredibly frail and kept fainting. Eventually I chose to replace it before it gets angry at me and can maximize Frustration, lmao. I settled for Deino, which I thought was a pain when I first looked over it, having Hustle and all, plus evolving at Level 64, which was another pain, since all the Lucky Egg + Exp. Share pointspam were starting to wane. Eventually it evolved into Hydreigon, and...let's just say, I was pretty proud to own a pseudo-legendary instead of that shameful Haxorus. Now Eelektross...pretty much the same kind of story as Zoroark, except now with Galvantula and his outrageous speed plus STAB Thunder + Compoundeyes, but again, it was incredibly defenseless, so I went to getting Tynamo, since I don't really like Stunfisk or Zebstrika. I had the same problem with levelling up, with the whole Thunderstone shaboom and whatnot, but it all payed off with an Speed EV trained Eelektross. Though its defenses are low, they still aren't as weak as Galvantula's, plus its Atk and Sp. Atk are quite higher, so it all works out.

Now, I might train a Ferrothorn for my next team, and a Chandelure, two Pokemon I never even bothered with lol.

 

[Rooke]

I never thought I'd use any other Flying-type than Unfezant whenever I played through Black. I wanted a change for one of my playthroughs, though, so I ended up with a Swoobat, and I love it.

 

[Numbers]

The Ice cream Pokemon. When I first seen it I hated it. I said I would never use such a Pokemon as it's design is so *Quack*-ing stupid.
Then I really needed an Ice type in my team and thought, "What the hell, I'll use it then switch it out later."

I now love this Pokemon.

 

[deoxys121]

How about Woobat and Swoobat? I always hear about people dissing them for having relatively low stats and being some of the most ugly Pokemon ever (which I agree on the ugly part). But, Swoobat has been a great partner to me. The Psychic/Flying typing is a great combination, and like all Psychic-types, they have a very wide move pool. Just look at my signature. My Swoobat from that playthrough (I started over again with Oshawott as a starter, and a completely new team) knows Psychic, Air Slash, Energy Ball, and Shadow Ball, and can really pack a wallop.

 

[Amore]

Yeah...Zubat's family. It only ever reached Golbat, but god knows why I was using it on Platinum...

Slowpoke is another one. The furthest I've ever gone through with one is having a Lv.38 Slowking in SoulSilver, before I got rid of it, but I'm always intending to use both Slowbro and Slowking once (probably in LeafGreen and HeartGold). They look cool, and are useful, so I now want them. Part of the reason I didn't think I'd use it is that up until I got LeafGreen in '08, I'd never even seen one in-game...

 

[Seki]

Psyduck and Golduck, thought that it was a noob untill i had to use it in gym battle against Chuck in Soul Silver, and boy was I surprised. Used it as a surf slave, before getting forced to use it against Chuck.