OU Team, made in Gen IV

Woah...first RMT in the section. Hooray? Anyway, let's get this started. This team is for Gen IV, since I can't read Japanese and don't have B/W yet, but if there are any big 5th gen threats that are out there when I move it over, let me know. This team is built around using a Poison Heal Breloom as a physical sweeper, with help from entry hazards

Crobat@Leftovers
Jolly nature EVs: 104 HP / 152 Atk / 252 Spe
-Brave Bird-Taunt-Roost-U-turn

Fast lead, prevents rocks from getting set up. Brave Bird and Roost make a pretty good combo, U-turn lets me get out if I need to. Leftovers gives me a little bit of bulk. I chose Crobat over a Stealth Rock lead like Areodactyl because Crobat outspeeds pretty much every lead BUT Areodactyl, and it has the ability to U-turn out of anything that does threaten it.

Forretress@Leftovers
Careful nature EVs: 252 HP / 4 Def / 252 SpD
-Spikes/Stealth Rock-Toxic Spikes/Stealth Rock-Payback-Rapid Spin

Forretress proceeds to either set up my own rocks or as many layers of some sort of spikes as possible to make things easier for everyone else. Also, if rocks do get set up, it can Rapid Spin them away. Payback punishes Ghost-types trying to block Rapid Spin and also keeps Forretress from being Taunt bait.

Dusknoir@Leftovers
Impish nature EVs: 252 HP / 28 Atk / 228 Def
-Wil-O-Wisp-Pain Split-Earthquake-Thunder Punch/Shadow Sneak

My main wall, and also my Spinblocker. Earthquake because something needs to carry it, Thunder Punch for Gyarados, or Shadow Sneak for STAB and priority.

Porygon2@Leftovers
Bold nature EVs: 252 HP / 216 Def / 40 SpA
-Recover-Charge Beam-Ice Beam-Thunder Wave

Pulls double duty as a tank and a charging special sweeper. Charge Beam not only gives me boosts, but BoltBeam coverage. Plus, Porygon2 is bulky enough to take a couple hits as it charges up and then Recover it all away. Thunder Wave spreads some status around.

Breloom@Toxic Orb
Adamant nature EVs: 4 HP / 252 Atk / 252 Spe
-Spore-Substitute-Focus Punch-Seed Bomb

The crux of this team. This guy stays, no matter what. Pretty standard set, but it works wonders.

Gyarados@Leftovers
Adamant nature EVs: 156 HP / 72 Atk / 96 Def / 184 Spe
-Dragon Dance-Taunt-Waterfall-Stone Edge

Secondary physical force, with a bit of bulk to help take hits and Dragon Dance to dish them back out.

First off, I want to say that I had a full analysis of this team, which was cruelly destroyed by random Web Browser closing. Anyway...

Crobat, you may want to consider Super Fang. Ninjask, Electrode, Acelgor, and most offensive Choice Scarf leads are your enemy.
Foretress, you may want to consider Gyro Ball over Payback, because most speedy Pokes switching in will hate you for it. Also know that all of your Hazard laying and removing lies soley on Foretress. Maybe not the best idea.
Dusknoir shouldn't have HP investment with Pain Split. Dump it in Sp.Def, be awesome. Screw Earthquake/ThunderPunch, try Toxic to Status everything except Heatran and Natural Cure Pokes, or Confuse Ray to be a real jerk.
Porygon 2 should forget Charge Beam because +1 Charge Beam does less than +0Thunderbolt (and Discharge for that matter). Try Download, Tri-Attack, Discharge, and Ice Beam.
Breloom is better in 5th Gen with Technician, and so is Gliscor with a superior Poison Heal in my opinion. Corbat will love to make this Breloom Set-Up fodder if its one of those never seen Nasty Plot sets. Maybe consider Facade on this Breloom.
Gyarados has Taunt too? Probably a bit repetitive. Also, it just seems like a very random attempt to add more raw power, and probably won't work well considering the lack of synergy the team has.

Lead Azelf and Infernape destroy you, period. Psychic, Fire Blast, and Thunderbolt from Choice Scarf Azelf will out-speed and OHKO 4/6 of your party, and do a whole lot to the rest of your team. Infernape can also be Choice Scarf'ed and have Fire Blast, Stone Edge, and Close Combat and take out 5/6 of your party the same way. The only thing it has to do is switch out to get past Gyarados' Intimidate. Dusknoir is no pushover, but it's certainly something almost any 5 other Pokemon can handle, especially considering Azelf and Infernape are common leads even in 5th Gen.

Breloom is supposedly the center-point of the team, yet next to none of its weaknesses are covered. Thunder-Wave on Porygon 2 helped with Breloom's mediocre Speed, however it should be something spread about the team, not just demanded upon one part of it. Hazards help as well, but Foretress has the same flaw of holding too much responsibility.

All in all, I say Dusknoir and Gyarados are out of place, and should be considered for replacement. I know Heatran is a great partner for Breloom, resisting ALL of Brelooms weaknesses, and almost vise-versa (almost being Heatran's Fighting-Type weakness, which is covered by Crobat just fine). Heatran can also set up Stealth Rock, as well as spread Burn and Toxic about the opponent's team (however, I think Hazards and Paralysis should be top priority).

Speaking of Priority, Breloom with Focus Punch IS powerful, yes, but as I said, its Speed is so-so. Mach Punch should be highly considered considering you're trying to make it a core of your team.

Leftovers is useful, but not the only item in the game. This game begs for a Choice Scarf Pokemon, which realistically could be Heatran, being able to come in, set up Stealth Rock to feign a Life Orb or Focus Sash maybe, and come in later game and revenge kill with Lava Plume, Earth Power, and oh, I don't know, some Hidden Power you think would be useful.

--TLDR;--

Needs improvement, but I would judge that as you test it out with the new Generation as you start getting into it. Find out where you wish you would have had something else, and fix it where need be.