Minato is in the last coffin i think.

[Sharinnigan]

i think it could be minato, because although people think it was the dead demon that made the 3rd coffin fail (in oro's fight with the 3rd hokage)
it was actually the 3rd who stopped it from being summoned, he even specifically says "i cant let that third coffin be summoned" because he knows minato would whoop his ass..however i do have mixed feelings about this only because i believe it could also be izuna uchiha..well see ^^

 

[leezagboola]

geez, not this crap again.
And with orochimaru summoning him, it was only in the ANIME and they probs hadnt even decided that he died using the dead demon seal.