Arbok Analysis

Arbok
Intimidate
Lowers the foe's Attack 1 stage. Decreases wild encounter rate.
Shed Skin
30% chance to heal status.
Type Tier
Poison NFE

Name Item Ability Nature
Choice Band
Choice Band Intimidate Jolly
Moveset EVs
~ Gunk Shot / Poison Jab
~ Earthquake
~ Crunch
~ Seed Bomb
56 HP / 252 Atk / 200 Spe
A powered up Gunk Shot is really quite scary (if it hits) and Earthquake and Crunch provide excellent type coverage alongside it. Poison Jab is a viable option over Gunk Shot if the 70% accuracy of Gunk Shot is a turn off. In the last slot, Seed Bomb, is Arbok's best option against bulky Water or Ground Pokemon such as Gastrodon, Quagsire, and Relicanth. While Aqua Tail will hit Ground types slightly harder then Seed Bomb, Seed Bomb is overall the superior option for its ability to take out combination Water / Ground or Water / Rock Pokemon. Pursuit is good for chasing down a fleeing opponent and could work in place of Seed Bomb, but the coverage given by Seed Bomb is a bit too good to pass up.

With these EVs, Arbok hits 270 Speed, beating neutral Toxicroak and Jolly Solrock.

Name Item Ability Nature
Neurotoxin
Leftovers Intimidate Impish
Moveset EVs
~ Glare
~ Poison Jab / Gunk Shot
~ Earthquake
~ Rock Slide / Crunch
252 HP / 4 Atk / 252 Def
This set takes advantage of two of Arbok's underutilized assets, Glare and Intimidate. With these EVs and Intimidate, Arbok actually takes physical hits better than Weezing (albeit with a Ground type weakness). This fact allows it to comfortably counter the top Fighters of UU, bulky Grass-types, Scyther, and Drapion.

The real magic of this set, however, comes from Glare. With no way to trap the Pokemon you're countering, expect to see a lot of switches, particularly to Special attacking Pokemon. Where Weezing's status of choice would be useless against these Pokemon, Arbok's Glare cripples sweepers from both ends of the spectrum, as well as those thinking that they have a free switch under normal circumstances like Venusaur. Glare also has the added bonus of being able to paralyze anything it hits, regardless of type. Unfortunately, it does come attatched to a not-so-hot 75% accuracy.

The attacks chosen give Arbok the best coverage available. Poison Jab and Gunk Shot make up its main STAB, with the former having a lower base power and the latter losing considerable accuracy to land a harder hit. The two other attacking moves round out coverage on types that Poison attacks can't hit. Earthquake hits incoming Steels and Drapion for Super Effective damage, while Rock Slide allows Arbok to hit Drifblim for Super Effective damage when they attempt to switch in and resist your Poison attacks. It also allows Arbok to hit Scyther harder, as well as Altaria. Crunch can be an option over Rock Slide if you feel that you really need to hit Rotom harder then Rock Slide. The final slot could also be replaced with one of the elemental fangs, but their damage output is rather lackluster in comparison, especially without any boost to Arbok's Attack stat.

Other Options

Not much. It has all the elemental fang attacks (Thunder Fang, Ice Fang, Fire Fang), but they're too weak to offer any kind of useful type coverage. Gastro Acid isn't worth a moveslot most of the time, but it can be helpful to rob some Pokemon of their ability.

Stockpile, Rest and Shed Skin can help Arbok tank a little, but with such a low HP stat and weak defenses, it will rarely prove effective.

EVs

You could move a few HP EVs into Speed to outspeed further Pokemon in the first set. 274 beats Jolly Absol, although it often has Sucker Punch, so your Speed advantage will be lost.

Opinion

Arbok is really a one trick pony ... snake. Use the listed movesets or use another Pokémon. It does not fit any other role adequately. Intimidate is a handy ability, but forgettable Defense and HP undermine it. However, it can switch in to the odd physical Fighting, Poison, or Bug attack.

Counters

Claydol, Solrock, and Lunatone can switch into Gunk Shot and Earthquake, but Crunch and Seed Bomb will leave a dent in them. Steelix will easily survive Earthquakes and switches into Gunk Shot, Crunch, and Seed Bomb quite easily. Bulky Ground-types like Sandslash, Quagsire, and Golem can switch in; but beware of Seed Bomb.

More sweeper-oriented switch ins must be careful to not switch into a Glare as the paralysis could cripple their sweeping intentions.