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 an OU standard, 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. Lapras has several advantages over Articuno as an Ice-type, with higher HP stat and much better coverage and utility with Confuse Ray, Body Slam, and Thunderbolt. However, even Lapras 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.
The best way to get Articuno on the field is to switch it in when you predict that your opponent will switch in Exeggutor; if it has lost over 33% of its health already, Blizzard is a guaranteed KO. It can also switch in on a predicted Earthquake from Snorlax or Tauros, dealing heavy damage with Blizzard and hopefully causing a freeze. Rhydon and Golem are a bit harder to switch in on, as Rock Slide will KO Articuno, but if you are fortunate enough to switch in on Earthquake, Blizzard will OHKO either. Double-Edge does chip damage to Lapras, who laughs at a 4x resisted Blizzard, as well as Starmie. Don't use Double-Edge against Chansey though, as it only does 5% more than Blizzard, causes recoil, and does not have a freeze chance. Don't use Agility until the late-game, when the remains of your opponent's team are within KO range. Finally, Hyper Beam is there to finish off weakened Chansey and Alakazam.Team Options & Additional Comments >>>
With Articuno's barren yet focused movepool, there are very few other options it can run. Mimic is probably the best unlisted option, as if Articuno gets lucky enough to copy Thunderbolt from Starmie, it will always 2HKO back. Reflect is another option to help Articuno absorb Body Slam from Snorlax and even Rock Slide from Golem and Rhydon should it find itself paralyzed against them. It also helps Articuno win against Tauros, who needs Body Slam critical hits to win. However, it is typically only useful when your opponent's special walls are gone, as they don't care at all whether Reflect is up.
Checks and Counters
Although Articuno's Blizzard is a frosty nuke and no Pokemon enjoys a freeze, there are quite a few solid counters to it. Lapras is the best Articuno counter, as it 4x resists Blizzard. Once it's in, it can wear down Articuno with repeated Thunderbolts or Body Slams or, if it has a free turn, use Confuse Ray on a switch-in. Everything about Starmie makes Articuno's life difficult. It 2x resists Blizzard and can attack with repeated Thunderbolts, paralyze either Articuno or the switch-in with Thunder Wave (except for Rhydon and Golem, who have no business facing a Starmie anyway), and then use any free turns to Recover. Cloyster also 4x resists Blizzard and has a ton of physical bulk, allowing it to absorb any physical attacks that Articuno might be running, then threaten either Articuno or a switch-in with Clamp, Blizzard, or Explosion. Chansey is as good a special wall as ever, paralyzing Articuno while firing off Thunderbolts or recovering with Softboiled, but it should be healthy and preferably paralyzed to block a freeze. It also takes 37.9 - 44.6% from Hyper Beam, so it has little hope in getting the chance to use Softboiled if its health is low. Alakazam can also use Thunder Wave, Recover off any damage, and spam Psychic until Articuno eventually faints, but it is 3HKOed by Blizzard, providing it with little time to do all of these things. Finally, Slowbro is a decent Pokemon to send out against Articuno one-on-one because it can paralyze it with Thunder Wave, but switching in is not recommended because it takes about 50% from two Blizzards before it even has a chance to move.