Manaphy
Deserves Testing.
Mew
IMO, belongs in Ubers. Don't get me wrong, I'd LOVE to start using my Uber Baton Pass team in OU (just replacing Dialga) and make everyone run Sandstream leads to counter it, plus I wouldn't have to worry about Arceus or Taunt Mewtwo. But really, Mew supports the team way too well.
Ho-oh
This is one I might consider for OU Testing, but it will probably remain Ubers. Sacred Fire with its 50% Burn rate is just way too good.
Palkia
Probably uber.
Dialga
Again, probably Uber.
Darkrai
IMO, Definitely Uber. Dark Void is just way too good with those stats and movepool.
Deoxys-D
This seems to be getting some controversy, so I'll say that I'm firmly in the camp that Deoxys-D definitely belongs in Ubers. People comparing it to Cresselia are WAAAAY off base. They have the same typing and comparable defenses (Cresselia has higher HP, Deoxys-D has higher Defense and Special Defense stats), while Cresselia has the better ability. However, Deoxys-D has a HUGE FUCKING MOVEPOOL.
First and foremost, Deoxys-D has Recover, which is a huge step up above Moonlight, meaning it can carry a reliable Recovery move that isn't fucked over by Sandstorm, the main drawback of Cresselia, who's usually forced to run Rest/Sleep Talk as a result.
Then we have the fact that Deoxys-D is literally the ultimate support Pokemon. It can not only Thunder Wave like Cresselia can, and throw up both Reflect and Light Screen, but it can also do a whole lot of other shit as well. It has access to Spikes, Stealth Rock, AND Toxic Spikes. It can Toxi-stall really well, which goes in tandem with the fact that it's also a fairly fast Taunter. And the one stat that many people seem to forget is Deoxys-D's 90 Base Speed Stat, making it faster than the majority of Taunters that can safely switch into it (anything faster with Taunt risks getting hit hard).
Then we have the fact that it can Cosmic Power, raising its Defenses almost to the point where it'd be almost impossible to take down since he also has access to Recover. Not to mention it can also Calm Mind as well.
And then let's not forget its offensive movepool. It learns all the things Cresselia can learn, plus a whole lot more. Superpower makes it so that Tyranitar can't safely switch in all the time like it can against Cresselia. Kind of busy right now, I'll get back to all the other shit it can do later (I did this one last)
Kyogre
Hell fucking no, and the reasons have already been stated on this topic.
Wobbuffet
Meh, I personally think Wobbufet is too good for OU. Annoying as fuck and just too effective at what it does.
Lugia
No. Haven't read through the entire topic yet, but the reasons should already have been stated, and I don't have time to write all my opinions down. Really though, it's the best wall in the game.