Articuno

Boasting one of the highest Special stats in the game along with the most powerful special move in OU, Blizzard, there's no denying that Articuno is a powerhouse. OHKOing Golem and Rhydon and 2HKOing Exeggutor are feats few Pokemon can muster, but Blizzard allows Articuno to do just that. It can force switches and deal heavy damage throughout the match, softening up your opponent's team and possibly causing a freeze. It can even make for a very nice end-game sweeper by boosting its mediocre base 85 Speed with Agility and blasting away with its STAB Blizzard, potentially getting a freeze in the process.

Why isn't Articuno more common, then? Again, its Speed stat is frustratingly low, as it is not able to outspeed Pokemon like Tauros and Alakazam without a boost, while both are capable of paralyzing Articuno. It is walled to kingdom come by the many OU Pokemon that resist Blizzard, namely Lapras, Starmie, Cloyster, and to an extent, Slowbro, as well as Chansey with its massive 250/105 Special bulk. Its movepool is shallow as well, as it leaves Articuno relying on mediocre Ice / Normal coverage, the latter of which runs off its so-so Attack stat. Other Ice-types such as Lapras and Cloyster are generally preferred, due to access to helpful moves such as Thunderbolt and Explosion respectively. However, they can never dream of matching the raw power of Articuno's Blizzard. All-in-all, if you are looking to unleash a nasty surprise on your opponent, don't overlook Articuno.