Mhmm... Say Naruto times it perfectly with a Rasenshuriken and Oro takes it. I'm sure he could get around it somehow... but that could mess his body/Chakra Network up... thoughts? :/
Eh, not "immunity" in that sense of the word, but most ninjutsu would have little effect on him...Orochimaru can take hits from tons of things and get away unharmed..and he knows this...
but there are things he knows even he can't withstand.. such as tbb..he stated " even for me...getting hit with that would spell out certain death..."
Well he can survive getting cut in half just fine it seems. Plus he can just regrow lost organs or appendages just by shedding his skin.. I think it's safe to say that not much can actually kill the guy. Heck he was just revived after getting sealed by the Sword of Totsuka. Still there are some pretty powerful techniques out there that CAN get the job done.