Well I've just finished a run of White 2 and I'd like to nominate
Skorupi for High Tier. I honestly feel it should be somewhere between high & mid but I had to pick one and there are a couple Pokemon I feel Skorupi competes positively with in high tier.
The reservation list states that Skorupi is done, but I don't see anything in the OP, so I'll fill this out just in case as well as to explain my points.
Name: Skorupi
Availability: Mid-Late game, Reversal Mountain, Level 35-37 in Dark Grass, 3 levels from evolution.
Stats: Skorupi's Base 90 Def, poisoning, and berry-stealing makes it pretty mindless to Audino grind those 3 levels. Drapion has a great base 95 speed, high base 110 Defense, and a solid Base 90 Attack. It usually attacks first, even with a neutral nature, and can survive anything but a STAB Earthquake.
Typing: It's Poison/Bug to start out, but that lasts for about 5 minutes. It evolves to become one of the dime-a-dozen late-game Dark-types as well as a common Poison-type but it only has one weakness; Ground. Poison resistance & poison-status immunity are fantastic late-game but just be mindful that Earthquake is common in the final stretch of the game.
Movepool: Gets Night Slash right before evolution and always has Hone Claws when caught. All the Elemental Fangs are available via Move Reminder for one Heart Scale each, giving it a Physical BoltBeam as well as Fire Fang for coverage. It gets Crunch around Victory Road at level 49. X-Scissor can take other Dark-types out faster. It struggles with Steel-types initially but learns Bulldoze, Dig, and the previously mentioned Fire Fang to cope. However, Drapion is pretty much forced to switch against a Ground-type not x4 weak to Ice.
Major Battles: Ice Fang and its Defense stat can help with Drayden's Gym and Marlon's Gym has plenty of Water/Flying-types clipped by Thunder Fang as well as a Starmie and Marlon's own Jellicent begging for a Night Slash. Drapion walls and runs through Team Plasma and sweeps half the Elite 4 as they struggle to even touch it.
Additional Comments: Drapion is a contender for the most coverage you can get in the main story. Its stats let it function as a fast tank that, depending on the nature, can hit pretty hard. It may not hit the hardest with its coverage moves, but it is never hard-walled by anything and can stand its ground. Battle Armor makes crits a non-factor, which is fantastic for Hone Claws setup, and Sniper pairs well with Scope Lens and Night Slash for consistent and punishing crits. It can use Black Sludge as well so it won't hog your team's Leftovers like other Pokemon. It can also make use of Expert Belt as it can nail most Pokemon super effectively for an easy 2HKO. Speed and coverage are definitely its biggest selling points as Aggron can play similarly against Plasma and the Elite 4 but lacks the Speed to sweep and Zoroark can sweep the same members of the Elite 4 but finds itself walled by many other Pokemon that Drapion would not. If you lack a full party by Reversal Mountain, Skorupi is a very solid pick.
I'd definitely call this guy the best in-game BW2 Dark-type. I've ran with Zoroark multiple times now and it hasn't been nearly as useful as Drapion. You get it 2 gyms later than Zorua, but Zoroark isn't very useful until after you have access to Drapion outside of the couple Sigilyph you face in Skyla's Gym in challenge mode (and Celestial Tower, but that area is entirely optional anyway once you get the Lucky Egg on the 1st floor and only contains two very '
meh' TMs). Unlike Zoroark, you don't have to grind PWT or Subway for an hour to get a half-decent coverage move; all it costs is a few Heart Scales that the game liberally throws at you (I had 3 by that point without even looking for them) and you have Physical BoltBeam + Fire or Ground coverage. No Battle Points, no Shards, no time wasted. You have access to Expert Belt even before you get Skorupi so Drapion's base 90 Attack stat becomes significantly beefier because there are so many Pokemon Drapion can hit super effectively. It's very versatile and it becomes a team player with a completed coverage move-set after 3 levels with wild Audino in the same area. It's one of those very few mid-late game Pokemon that's not only good, but it can get going right out of the box.