I think you guys are overlooking one very important new weapon in Arcanine's arsenal: smooth over. It allows him to combat his fellow fire types with efficiency (super-effective hits deal the same amount of damage as a neutral close combat), and its secondary effect lowers the opponent's speed by one stage. Now Arcanine's not slow, but as others have stated, there are those that can do the fast fire/fighting combo better, such as Infernape, speed boost Blaziken, and encourage Hihidaruma.
What separates Arcanine from these guys are Arcanine's impressive defensive stats, intimidate, and extremespeed. As such, he's probably best off acting as a bulky physical attacker, not an all-out life orb attacker or a choice user.
intimidate/heart of justice @ shell bell
adamant - 252 atk, 144 spe, 112 hp
~ flare blitz
~ wild bolt
~ smooth over/close combat
~ extremespeed
Max attack for hurting things, enough speed to outrun neutral base 80s and max speed adamant Gyarados, with the rest in HP to give him some bulk and cope with recoil damage. Shell bell is recommended since you're going to be attacking every turn, and it heals more than leftovers on really hard hits (such as OHKOing something). Also, you receive the HP right after your attack, rather than waiting till the end of the turn. This helps add to Arcanine's survivability (not by much, but it's still something). With smooth over and extremespeed, Arcanine doesn't need max speed to perform well, and the extra HP goes a long way in helping him hang around.
I personally like intimidate better on this set. It adds to Arcanine's bulk, and there are A LOT of terrifying physical attackers in the fifth gen. Simply having something with intimidate can make the difference between a win and a loss. However, heart of justice is also a cool ability for potentially scoring an attack boost and (presumably) adding an immunity to dark attacks.
Smooth over lets him take on Shanderaa (the chandelier) without resorting to wild bolt, and other fire types without lowering his stats via close combat. It's also a MUCH better choice against Heatran. Close combat will squander Arcanine's bulk by lowering his defenses, whereas smooth over slows your opponents down. Consider: a non-boosted close combat/smooth over will NEVER OHKO a Heatran that doesn't have a defense lowering nature. The same could be said for Heatran's earth power against Arcanine (if you don't believe me, run the figures). Naturally, the faster of the two would be the victor - so if you slow Heatran down on the first turn, you can easily pick him off on the second. Smooth over can allow you to get 2HKOs you wouldn't otherwise achieve, and also acts as a useful scouting tool. For instance, if you catch something like life orb Starmie with smooth over on the switch, you can easily finish it off with wild bolt (whereas flare blitz/close combat + extremespeed might not be enough). If you're worried about choice scarfers, just add some more speed. 212 speed EVs will let you outspeed naive choice scarf Heatran after the first smooth over. 248 EVs will let you outrun jolly Gyarados. Neither will OHKO you at full health, though, so I see little reason to go beyond 144 speed EVs.
However, if you're really scared of Tyranitar, close combat is still a viable alternative. And I guess it's nice to be able to KO Blissey without sacrificing a ton of health. Arcanine also struggles against Sazando (the dark/dragon that looks like King Ghidorah) if he lacks close combat, but Sazando outspeeds him anyway, so if he wants to hit you with a draco meteor or earthquake, he's probably going to do so. Your best response would still be to either switch or chip away at him with extremespeed. You can also run overheat somewhere to beat physical walls, but to reiterate an earlier sentiment, there are others that are better at this.
What separates Arcanine from these guys are Arcanine's impressive defensive stats, intimidate, and extremespeed. As such, he's probably best off acting as a bulky physical attacker, not an all-out life orb attacker or a choice user.
intimidate/heart of justice @ shell bell
adamant - 252 atk, 144 spe, 112 hp
~ flare blitz
~ wild bolt
~ smooth over/close combat
~ extremespeed
Max attack for hurting things, enough speed to outrun neutral base 80s and max speed adamant Gyarados, with the rest in HP to give him some bulk and cope with recoil damage. Shell bell is recommended since you're going to be attacking every turn, and it heals more than leftovers on really hard hits (such as OHKOing something). Also, you receive the HP right after your attack, rather than waiting till the end of the turn. This helps add to Arcanine's survivability (not by much, but it's still something). With smooth over and extremespeed, Arcanine doesn't need max speed to perform well, and the extra HP goes a long way in helping him hang around.
I personally like intimidate better on this set. It adds to Arcanine's bulk, and there are A LOT of terrifying physical attackers in the fifth gen. Simply having something with intimidate can make the difference between a win and a loss. However, heart of justice is also a cool ability for potentially scoring an attack boost and (presumably) adding an immunity to dark attacks.
Smooth over lets him take on Shanderaa (the chandelier) without resorting to wild bolt, and other fire types without lowering his stats via close combat. It's also a MUCH better choice against Heatran. Close combat will squander Arcanine's bulk by lowering his defenses, whereas smooth over slows your opponents down. Consider: a non-boosted close combat/smooth over will NEVER OHKO a Heatran that doesn't have a defense lowering nature. The same could be said for Heatran's earth power against Arcanine (if you don't believe me, run the figures). Naturally, the faster of the two would be the victor - so if you slow Heatran down on the first turn, you can easily pick him off on the second. Smooth over can allow you to get 2HKOs you wouldn't otherwise achieve, and also acts as a useful scouting tool. For instance, if you catch something like life orb Starmie with smooth over on the switch, you can easily finish it off with wild bolt (whereas flare blitz/close combat + extremespeed might not be enough). If you're worried about choice scarfers, just add some more speed. 212 speed EVs will let you outspeed naive choice scarf Heatran after the first smooth over. 248 EVs will let you outrun jolly Gyarados. Neither will OHKO you at full health, though, so I see little reason to go beyond 144 speed EVs.
However, if you're really scared of Tyranitar, close combat is still a viable alternative. And I guess it's nice to be able to KO Blissey without sacrificing a ton of health. Arcanine also struggles against Sazando (the dark/dragon that looks like King Ghidorah) if he lacks close combat, but Sazando outspeeds him anyway, so if he wants to hit you with a draco meteor or earthquake, he's probably going to do so. Your best response would still be to either switch or chip away at him with extremespeed. You can also run overheat somewhere to beat physical walls, but to reiterate an earlier sentiment, there are others that are better at this.
