Each of the tiers?
If you need the list of the pokemon in the tiers (Never used-NU, Under used-UU, Over used-OU,Border line-BL, Uber), go here http://www.smogon.com/dp/pokemon/

Me? well...
NU: Pachirisu
UU: Lanturn
OU: Smeargle (how is it OU?)
BL: Abomasnow
Uber: Wynaut (just, no)

NU Delibird
UU Umbreon
BL Yanmega - Really come on it's x4 weak to stealth rock.
OU Bronzong
Uber Wynaut

NU: Corsola
UU: Qwilfish. (OLOLOL just noticed this thing got into UU xD)
BL: Yanmega ( I thought about saying Abomasnow but the thing can surprisingly cause lotsa grief...well for my breloom atleast. One of the few pokemon that fully counter my Sash-loom)
OU: Ninjask (Predictable baton passer is predictable. :V)
Uber: wynaut (Why is he here? :l

NU: Unown. Can't get much worse than Unown.
UU: Hitmontop, though Qwilfish is also bad. Lanturn I find is a very useful pokemon.
BL: It's a really small tier and they're all pretty good, but I pick Yanmega.
OU: Realistically Smeargle, but Lucario because I hate him
Uber: Again, Wynaut is accurate, but I hate Dark Void Darkrai. Other Darkrai is all right

NU: Unown. I searched the whole list, and EVERY OTHER POKEMON CAN FIND SOMETHING TO DO, unlike this guy.

UU: Poliwrath. I think this guy was moved to UU because of how good he was in NU, but that doesn't make him great in UU. And how can you say Qwilfish is bad? Put him on a Rain Dance team and watch.

BL: It's a small tier, and I say Abomasnow. Though Yanmega loses half of its HP to Steath Rock, Choice Specs and Tinted Lens and rip through even things that have a resistence to Yanmega's moves. Abomasnow has 7 weaknesses, many of them relativey common.

OU: Dusknoir. Rotom-A has pretty much made this guy worthless as a Spin Blocker, but he's still too strong to be moved down.

Uber: Wynaut. Wobbuffet can do the exact same things he can, only better.