Sorry if a thread like this already exists.
I will sometimes use a Pokémon that I'm not really expecting to be very good overall just because it's the most convenient way to do something, or because I'm looking for a change of pace. I picked up a Geodude and trained it up in HG even though I knew it wasn't going to be that strong because I needed Ground coverage and it was the most readily-available thing, for example. Occasionally, I'll be surprised by the strength or general usefulness of one of these Pokémon, and this thread is dedicated to those unlikely playthrough heroes.
To get us started, I'd like to talk about Umbreon in White 2. In my most recent playthrough, I picked up an Eevee in Castelia City and evolved it into an Umbreon because it seemed like it would fit well on my team, but I didn't really know what to expect from it. Due to incompetence, I wasn't able to evolve the Eevee until it had missed the opportunity to get Faint/Feint Attack, and I was worried about Umbreon's damage output based on its stats. However, it actually ended up being very good anyway because I got the TM for Payback a little bit later. I gave Payback to Umbreon, and then gave it a Full Incense so it would almost always move last, which allowed it to deal a surprisingly high amount of damage, especially on Pokémon weak to Dark moves. I was a little worried that it wouldn't be able to sustain that damage output for long because it had to get hit every turn, but it has great defenses and was able to wall quite a few Pokémon after it got Moonlight. I also gave it Flash, and much fun was had cheesing stuff with that. Flash was probably the only reason I was able to beat Iris, because Umbreon was the only Pokémon on my team that could live an attack from Hydreigon and it was able to get enough accuracy drops for the rest of my team to exist on the battlefield without immediately being wiped off the face of the planet.
Overall, Umbreon was much better than I expected, and I would definitely recommend it for people who want to mix things up in B2/W2. What stories do you have of Pokémon that exceeded your expectations like this?
I will sometimes use a Pokémon that I'm not really expecting to be very good overall just because it's the most convenient way to do something, or because I'm looking for a change of pace. I picked up a Geodude and trained it up in HG even though I knew it wasn't going to be that strong because I needed Ground coverage and it was the most readily-available thing, for example. Occasionally, I'll be surprised by the strength or general usefulness of one of these Pokémon, and this thread is dedicated to those unlikely playthrough heroes.

To get us started, I'd like to talk about Umbreon in White 2. In my most recent playthrough, I picked up an Eevee in Castelia City and evolved it into an Umbreon because it seemed like it would fit well on my team, but I didn't really know what to expect from it. Due to incompetence, I wasn't able to evolve the Eevee until it had missed the opportunity to get Faint/Feint Attack, and I was worried about Umbreon's damage output based on its stats. However, it actually ended up being very good anyway because I got the TM for Payback a little bit later. I gave Payback to Umbreon, and then gave it a Full Incense so it would almost always move last, which allowed it to deal a surprisingly high amount of damage, especially on Pokémon weak to Dark moves. I was a little worried that it wouldn't be able to sustain that damage output for long because it had to get hit every turn, but it has great defenses and was able to wall quite a few Pokémon after it got Moonlight. I also gave it Flash, and much fun was had cheesing stuff with that. Flash was probably the only reason I was able to beat Iris, because Umbreon was the only Pokémon on my team that could live an attack from Hydreigon and it was able to get enough accuracy drops for the rest of my team to exist on the battlefield without immediately being wiped off the face of the planet.
Overall, Umbreon was much better than I expected, and I would definitely recommend it for people who want to mix things up in B2/W2. What stories do you have of Pokémon that exceeded your expectations like this?