Just a f-ed up idea that came to me today while chatting with some peeps on tumblr. We came up with a plausible theory: Madara is Tobi, but he's using Obito's body, and Madara's real body is in the 6th coffin.
It would explain why Tobi never shows his face, even though everyone (supposedly) knows who he is, why Kisame bit off his tongue before anyone could see Tobi take his mask off, and the fact that he has (had) only one eye.
The only hole in the theory is the fact that Obito's body was crushed.. but Kakashi and Rin... they never actually recovered it and Madara could have found it and somehow used the 1st hokage's DNA to reconstruct the body.

Slight problem about that, 'Tobi' had both sharingan when he fought Konan.

However since Tobi seems to be able to regen arms with some method, its not impossible that he regen'd Obito's broken body and implant another sharingan into the left eye socket.

I don't know why people think its Obito just because Tobi is an Uchiha. Obito got crushed by a boulder, had one eye removed and died so the chances of him turning out to be the main villain is slim to none. I believe there is a chance that Tobi is not Madara but it is very unlikely that it is Obito.
I believe the three most likely people to of been in that coffin are Madara Uchiha if he is not Tobi, Izuna Uchiha or Rikudou Sennin.
Also why would Madara specifically go after Obitos body and go through the trouble of reconstructing it? There were still Uchiha at that time so if he needed a body he could of gotten a much better and healthy one, Obito was a dead, below average ninja so it wouldn't of made sense to go after him.

Anyway Tobi showed his face to Kisame remember and Kisame called him Mizukage (Madara was the former Mizukage)

You all wait. You will see. And I will be laughing it up in your faces. Tobi is Obito. Well, maybe not Obito, but he's definitely not Madara. I'm right. I just know it. You will ALL see.

I bet 5 props that it isn't Obito XD There are too many facts that point away from him, we might see Obito again in the story either as a flashback or an Edo though.

Lol you are on. Tobi being Obito does not make sense, I agree, but we have not seen any actual proof Tobi is Madara aside from the fact that he SAYS he's Madara. I think more facts point away from Madara than they do Obito. Basically, Tobi could be anyone.

Plus, if you add an o and rearrange tobi, you get obito. Probably coincidence but it's reminiscent of I Am Lord Voldemort = Tom Marvolo Riddle XD (Kishi has said he likes the Harry Potter series after all)

Haha I see what you mean although we do have one bit of proof and thats when he showed his face to Kisame and Kisame called him Mizukage. There are a few other moments but that is probably the biggest in favor of Madara.
Anyway he wouldn't keep his mask on if everyone knew who he was so I wouldn't be surprised if it was someone else and not Madara.

Tobi could be obito, or rin, or even donzo. No body know except kishi. Who knws it could even be donzo. Or even a totally new character. All we can do is wait

Why am I the only one what still thinks tobi is madara...But of corse its not obito. Thats like saying itachi is tobi. I mean he could be someone else. but as for right now I think he's madara. unless i'm reading the manga wrong madara never died.
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madara has the rinnegan just like tobi how did he get it?? Madara knows kabuto is controling or what ever and is helping tobi
Go to the next page. There are so many signs to me that are tell us who he is and it all turns to tobi. Either tobi is madara or someone else.
but I really don't think he's someone else I mean why would someone else say i'm madara with all that power??

and on that obito thing again. His boy got crushed into peices I really don't think they would try to put his body back together did tobi or madara even know obito and in that coffin It was madara's body but when madara was fighting the 1 first he did take some of his DNA we really dont know tobi's power so anything could happend he does have a most any power. and I seen his face already. Unless the pic is wrong

Forget it he's someone else..xD