Arbok is decent contender in UU; however, a shame it's walled by every Ground available.
This set is perfectly suited for UU play. Glare will paralyze anything besides a Ghost-types that switches in and will always be a great help; just watch out for that shaky 75% accuracy. Rock Slide can flinch stuff after you've Glared them, and Earthquake should take care of Steels and Rocks to an extent. Hopefully you will paralyze something fast like Gligar, but Sandslash doesn't like to be paralyzed either.
Here is a Choice Banding Arbok. Not really much an explanation is needed. He is decently fast, so he should be able to damage some things before biting the dust. Hidden Power Ghost has an accuracy advantage over Iron Tail, but if you're playing UU you may want to use Iron Tail to hit Solrock and Lunatone really hard.
Body Slam is great for paralyzing things with the Choice Band set, but can be used without Choice Band as well if you want to be sure to damage things. Giga Drain comes from below average Special Attack, but it will 2HKO Quagsire. Hidden Power Ice can hit Gligar HARD as well as any other Ground, but if you're into such mixed sets I suggest you check out Seviper instead, since he has much more Special Attack to work with.
Haze isn't going to do much since Arbok doesn't have the defenses or resistances for it, but if you're afraid of Baton Passing chains it's an option. Just use Shed Skin instead of Intimidate, then. This also applies to Rest; the only way for Arbok to use it effectively is by attempting to take advantage of Shed Skin's 33% chance to remove your status conditions at the end of each turn. You could also use Sleep Talk; Arbok is actually a pretty good sleep absorber in UU play to switch into Meganium.
Snatch can get you a Gligar Swords Dance if your prediction is paying off, but you're highly unlikely to kill them before they kill you with Earthquake. Thief stealing the Leftovers of something like Gligar can really win you the game, just don't equip Arbok with anything when using it.
As suggested, Arbok always wants max Attack to hurt as much as possible. If you're using Glare, there is no need to put a lot of Speed EVs. For UU, at least put 200 (not EVs, the stat) or so for outspeeding every kind of Meganium. With 240 you will outrun Poliwrath, Lunatone and Solrock that do not use a +Speed nature (which is nearly always), so that's good to stick with. If you still want to go with a speedy Arbok, use 270 to outrun Nidoking without a +Speed nature.
On a Choice Banded set, just max Speed and Attack and use Jolly. Killing is more important than surviving random hits.
Checks and Counters
Arbok is frail, so everything that uses Earthquake or Psychic instantly knocks him out.
There are not many Steels to wall it, but plenty of Rocks and Grounds that just as easily come in on Sludge Bomb and usually Earthquake. Main counters include Solrock, Lunatone, Golem, Sandslash, Quagsire, Omastar, and Gligar, all of which resist Sludge Bomb and take little to no damage at all from its other moves, though all of these except Gligar do not like Giga Drain much, and again Glare may hinder them. Iron Tail hits Solrock and Lunatone hard as well.
Poison-types like Muk, Nidoking, and Nidoqueen can come in on Sludge Bomb. Muk can Curse up and beat Arbok one on one, and Nidoking and Nidoqueen can hit hard with STAB Earthquake. However, they fear being Earthquaked themselves. Arbok needs Hidden Power Ghost or Rock Slide to touch Shedinja, so you can bring that in on the Choice Bander, or on the first set if it lacks Rock Slide for some reason.
Kangaskhan can hit Arbok hard with Earthquake and will probably beat it one on one, but it's not going to switch into these STABed Sludge Bombs. When facing Meganium using Arbok, always watch out for Counter.