Bumping this with 3 more anti metagame pokemon.
Spec'd Hydreigon is suprisingly really good. Unlike Spec'd Latios, people can't Pursuit it. That means you can play it much more aggresively than Latios. It also gets Flamethrower and Focus Blast. It resists dark which is pretty cool too. People usually expect Expert Belt and get nailed extremely hard by this. Works great with spikes from deoxys S.
Spec'd Kingdra is also extremely good right now. It can make short work out of rain teams with Swift Swim. It makes a great lead, checks Rotom W, checks Gyarados, checks Starmie, checks Volcarona, checks SD Scizor, and more. Works great with spikes. The suprise factor often leads to a suprise kill and Draco Meteor hits even steels extremely hard. Dragon/Water is still great coverage in BW OU, and you can use HP Fire for Ferrothorn. If used on a Rain team, Sniper is a great alternative because Swift Swim is illegal. Sniper allows you to crit Jirachi and Ferrothorn for OHKO's. When used on a Rain team it gets to abuse the water STAB much more, even 3HKOing Ferrothorn. Great with Jirachi or Dugtrio for team support.
Sigilyph is also really good too. Many teams are weak to it with the drop in Tyranitar usage. Most Rotom W lack Thunderbolt in favor of Volt Switch, which often means they need to Trick you to win. It gets Cosmic Power boosts at a frightening amount of the metagame. It spreads status to soften teams for an eventual sweep. It makes a great Scizor, Jirachi, and Tyranitar lure only for you to burn them. The metagame is also more physically inclined, which is good pickings for Sigilyph. More things to burn. It also destroys stall without CM Jirachi lol. You would be very suprised how easy it is to get +3 with it and start beating face.