Are people forgetting that a standard Taunt / DD Gyarados beats Revenankh every time? It can switch in on fighting attacks with ease, is quite bulky, intimidates, out-speeds and taunts Revenankh's plans to Bulk Up or Rest / Moonlight, and can Dragon Dance it its face. Power Whip is Revenankh's best chance, but it still isn't very strong.
Anything faster than Revenankh with Taunt that isn't weak to Ghost / Fighting basically beats it. Even Gliscor serves as a counter, as it's 4x-Ice weak can be cut in half with Roost, and it still has such astronomical defense that it can survive a hit and pummel on it. Knock Off hurts ShedRest pretty bad, as well. Muk also falls under Weezing's territory, but has Taunt in place of Haze.
Bulky Pokemon like Hippowdon and Donphan can simply roar it away if it doesn't have Taunt. Suicune can out-speed it, survive hits even after a few bulk ups, and Roar it away as well. Skarmory can easily Brave Bird / Drill Peck it and threaten Whirlwind, playing mind games with it. Most Revenankh forego Taunt, and those that do lose either coverage or bulk up.
Also, Taunt goes straight through Substitutes, so the SubPunch set is owned just as easily.
Togekiss really is the real deal. It can Wish to avoid Roost's side-effect. It obviously beats it with Air Slash. And, it out-speeds it and can Encore Bulk Ups.
Encore and Taunt are really the bane of any Revenankh, because left without recovery and Bulk Up, Revenankh is nothing but a vulnerable shell.
While Substitite blocks Leech Seed, it really annoys the typical set, as earlier stated. Salamence faces the fear of Ice Punch, but can Intimidate, resist Fighting-typed attacks, and hit it hard. This still dies to SpecsMence.
Zapdos with Metal Sound OR Charge Beam can beat it, as well. Metagross / Jirachi with Zen Headbutt to a number.
I will say that Shadow Sneak is amazing on this guy. All of the powerful special attacking threats that can overcome Revenankh's monstrous special defense and out-speed it -- Alakazam, Gengar, Azelf -- fall victim to it. Meanwhile, a lot of other main special attackers -- Heatran, Porygon-Z, Magnezone -- are weak to Fighting.
Don't forget Yanmega! Yanmega can actually come in quite easily on a Bulk Up or Hammer Arm, and can even take a Shadow Punch. It can then Protect, Hypnosis, and Air Slash it in the face.
If Wobbufet is is allowed in OU, it can come in on anything but Shadow Punch and immediately screw Revenankh up. It's bulky enough to withstand Shadow Sneak and Shadow Punch if it only has one or two Bulk Ups.
There are enough counters for this, I think. But, it definitely is a monster.