Alright, now I have looked through the rejected list and I tried to find a pokemon that could be useful in OU. Then I came across Arcanine. A physically defensive one with Intimidate, I might add. Now, I have thought of several reasons why it's bad in OU. First, it's weak to the common Edge-Quake combo. Yes, I do realize that this looks bad for a wall, but bear with me. First, I will present a replay using Arcanine.
http://replay.pokemonshowdown.com/ou-113782593 - I was told that Arcanine was out-classed by Landorus-T power-wise, speed-wise, and stat-wise. Alright, that's a very valid argument. For one, Arcanine doesn't have a blistering 4x ice type weakness. Another thing Landorus-T doesn't have is access to Will-O-Wisp, which is probably defensive Arcanine's greatest asset, being able to burn pokemon that would otherwise be able to take it out with a couple Earthquakes/Stone Edges. With pokemon around like Ferrothorn, Scizor, Mega-Mawile and Bisharp (just a few examples), Arcanine can find an opportunity to switch in and burn anything that they bring out to counter it. For example, Garchomp can normally stop Arcanine from doing much, but after being burned, it can barely even 3HKO Arcanine unless it holds a Life Orb or a Choice Band. Just to put them out there:
http://replay.pokemonshowdown.com/ou-113809311 and
http://replay.pokemonshowdown.com/ou-113817269 - I can see how Landorus-T can be more useful, but I think that's team dependent. Landorus-T has access to Stealth Rocks, U-turn, and a ridiculous attack stat while Arcanine focuses more on crippling the opponent's pokemon. One HUGE detail I forgot to point out is that Arcanine has reliable recovery in Morning Sun. This is a really big turning point, as Landorus-T has no reliable recovery whatsoever. Now Arcanine's typing would hinder it from doing it's job at first, due to a Stealth Rock weakness, but with the buff given to Defog, things got a bit easier for the blazing pooch. Arcanine can also finish off opponents with a +2 priority Extreme Speed, almost guaranteeing that Arcanine retains no further damage from the opposing pokemon before dying to burn damage. I have tried a couple sets for a physically defensive Arcanine, all with the same spread of 252 HP, 252 Def and 4 Atk or 4 SpD. One consisted of Substitute, Morning Sun, Extreme Speed, and Will-O-Wisp. Substitute is mainly for scouting out your opponents attacks and if they switch into a physical attacker, you can burn them, then switch out to something that can handle it. Rock Blast will bypass the substitute, so be wary of that. Some replays of Sub-Canine:
http://replay.pokemonshowdown.com/ou-113832032 and
http://replay.pokemonshowdown.com/ou-113836255 - I hope this can suffice enough to reconsider Arcanine. Really, I just want to make sure we don't miss out on any potentially great pokemon. Unlike the earlier tried Hitmontop and Machamp, I can easily do well with Arcanine in OU. I hope you can take it into consideration. Thank you!
Edit: Just a few calculations to show its usefulness (most special attackers will threaten Arcanine, so I will show physical attacking variants on common OU pokemon:
+3 252+ Atk Aegislash-Blade Sacred Sword (before being burned and at +4) vs. 252 HP / 252+ Def Arcanine: 249-293 (64.8 - 76.3%) -- guaranteed 2HKO after Leftovers recovery
-1 252+ Atk Conkeldurr Drain Punch (before a Guts boost) vs. 252 HP / 252+ Def Arcanine: 79-94 (20.5 - 24.4%) -- possible 6HKO after Leftovers recovery
252+ Atk Conkeldurr Drain Punch (after a Guts boost) vs. 252 HP / 252+ Def Arcanine: 118-141 (30.7 - 36.7%) -- guaranteed 4HKO after Leftovers recovery
-1 252+ Atk Life Orb Bisharp Knock Off (97.5 BP) (Arcanine will usually out-speed and burn the Bisharp, putting it at -1 after Defiant boost) vs. 252 HP / 252+ Def Arcanine: 122-146 (31.7 - 38%) -- 0.6% chance to 3HKO after Leftovers recovery
252+ Atk Gyarados Waterfall (after a Dragon Dance) vs. 252 HP / 252+ Def Arcanine: 234-276 (60.9 - 71.8%) -- guaranteed 2HKO after Leftovers recovery (Arcanine can then burn it)
+1 252+ Atk Huge Power Mega Mawile Play Rough (after 2 Swords Dances and a burn) vs. 252 HP / 252+ Def Arcanine: 173-204 (45 - 53.1%) -- 0.4% chance to 2HKO after Leftovers recovery
+1 252+ Atk Huge Power Mega Mawile Sucker Punch (after 2 Swords Dances and a burn) vs. 252 HP / 252+ Def Arcanine: 205-242 (53.3 - 63%) -- guaranteed 2HKO after Leftovers recovery (this is if you even attack using the Arcanine)
+1 252+ Atk Mega Scizor Superpower (after a Swords Dance) vs. 252 HP / 252+ Def Arcanine: 199-235 (51.8 - 61.1%) -- 96.1% chance to 2HKO after Leftovers recovery
If there are other calculations you want to see for this guy, then please tell me.