Because of all the new Pokemon introduced into the game by Black and White, there is now enough Pokemon to create a fourth tier, between Underused (UU) and Neverused (NU). With OU and UU lists determined (as with the start of any competitive Pokemon metagame, it is quite unstable, especially UU with V-Generate Victini and Kyurem), the new fourth tier is introduced, known as 'Rarely Used' (RU).


Read more here: http://www.smogon.com/forums/showthread.php?t=3448932

...Wobbuffet, Porygon-Z and Yanmega are all RU. And more.

RU isn't a tier yet. Most of the mods on Smogon are displeased with how R_D made that "tier" without any of their consent. I suggest you stay away from it instead of jumping right into it for the time being, at least, until it is comfirmed.

Well it's on the Smogon server so I don't see why anyone would need to 'stay away from it'.

Worst thing that happens is that you ladder for afew days and then they remove the tier. Not exactly a traumatic experience.

I for one am happy to see this, NU is still going to be huge this gen regardless of this tier, it's just going to give some other pokemon a chance to shine for once, as the pokemon that previously dominated NU will get their own tier, and NU will get a nice fresh new look. Everybody wins.

I have a question. Why do you let others decide what you can or can't use aside from the obvious legendaries like Mewtwo?

It's not letting people decide what you use. -_-

You use exactly what pokemon you want to use, use Mewtwo for all I care. The Meta-Game just gets broken down into Tiers so that the playing field is even. What would be the point of someone with 6 Ubers fighting against someone with six Never Used (NU) Pokemon? The ubers are almost guaranteed a victory.

Breaking down into tiers allows more pokemon to have a fair chance of being useful, let's more pokemon shine through and most importantly offers up variety in battle styles. Ubers and Over Used are dominted by weather (Ubers by Rain mainly due to Kyogre, Over Used by Sand Storm due to Tyranitar and Hippowdon). Under Used still has many weather inducers but isn't so centralised around weather with Hail really being the most prominent. Rarely Used will now have no weather inducers, so weather will be almost a non-factor.

Different Tiers, Different Dynamics, Different Challenges. More Diverse, More Fun.