Originally Posted by Fat superstar
In addition, I would like to nominate Ferrothorn for A-tier. It almost exactly fits the definition: Can wall many portions of the metagame and gives opponents free turns occasionally, but does his job most of the time. Ferro is a top 3 Pokemon for a reason: he consistently beats the threats he needs to and sets up hazards reliably. Sure, he can be set-up bait for some threats, but you can say that about Jirachi and Heatran as well, and no one is doubting their status there.
I am not sure if Ferrothorn really is an A-Tier Pokémon. Sure that all that is true, but Ferrothorn is having some problems on this new metagame. Before BW2, the most effective way to kill Ferrothorn was with Fire-type (and strong Fighting-type) attacks, and for this reason Ferrothorn was, and still is, found mostly on rain teams.
However, nowadays Ferrothorn is also dying to strong neutral attacks, so for the most part Fire and Fighting-type attacks aren't the only way to deal with the metallic jackfruit. Ferrothorn is dying to Landorus' Earthquake and Earth Power, to Tornadus-T's Hurricane, Genesect's Bug Buzz or Choice Band U-Turn, and many other things. Also, Ferrothorn is not really as good as a check to bulky Water-types. Despite being neutral at worst to most things that they could throw on them, such as Ice Beam, Ferrothorn has difficulty trying to actually defeat Water-types, first because it depends on a innacurate move to do this, and because many of them carry Scald. As Ferrothorn uses physical attacks, a burn renders him mostly useless against even bulky Water-types. Also, Keldeo is a Water-type that can actually defeat Ferrothorn 1x1 due to Secret Sword.
So, Ferrothorn can't really wall many portions of the metagame, but it is still an amazing Pokémon with acess to really good options, and is somewhat unpredictable. You never know wich entry hazard it is carrying; Stealth Rock, Spikes or both. You never know if it packs Thunder Wave, that can cripple you for the rest of match unless you are a Ground-type or have Volt Absorb. You never know if it is going to Leech Seed you to make you die slowy. You never know it it is carrying Gyro Ball to kill your fast, frail Pokémon.