I know this may be silly and I don't really feel like writing up a whole essay on why I feel this way, but of the many talented men of Inception that could possibly be noticed on a supporting actor level, my choice would be Cillian Murphy's Robert Fischer.
Granted, one hardly needs an Oscar nomination or win to be remembered and I won't be surprised in a few months when Inception will fail to put up any nominees in the supporting actor category (as it is, neither Leonardo DiCaprio for lead nor Marion Cotillard for supporting are anywhere near safe bets, but are likelier than anything else). I do believe, however, of all the interesting supporting actors featured within Inception, whenever Cillian Murphy was on screen, that's where my attention went, and it's not just because he's attractive, it's because he played the part so well and it really was a plum part amongst Ocean's Eleven type caricatures (which, though fun and well-performed and well-written, aren't exactly screaming emotional depth).
Whether or not he gets any awards attention, I simply wished to express the beautiful supporting performance Cillian Murphy put on for us all. He is quite a talented actor and I'll certainly be looking into more of his works thanks to a fantastic job in Inception.
And this is not a knock to any of the other supporting gents; you are all great. But, if I had to choose one, there's no real question about it. That scene in the third level of the dream, with his father, was nearly as touching to me as the entirety of Toy Story 3. Some might complain that Inception is heartless, but it's not, and Robert Fischer is that heart. You may say it does not count, because he is dreaming and asleep, but in the immortal words of Albus Dumbledore, "Of course this is happening inside your head, but why on earth should that mean it's not real?"
I've been quoting Harry Potter a lot lately. So shoot me.