I haven't seen Murder, Inc., so I will use this as a (very convenient) excuse not to vote, at least now (by coincidence, it will be on Italian tv soon). Peter Falk was, after all, a good actor, and this seems to be an intriguing, uncliched role for him.
Plus, I'm not sure, really. The best actor in this list is, by far, Peter Ustinov, and I will enthusiastically vote for him on his next nomination (one of the absolute best performances to win the Best Supporting Actor trophy, in my opinion). But as far as I remember his role in Spartacus isn't much more profound than, say, Hugh Griffith's in Ben Hur.
I'm not even considering Chill Wills. I could be tempted to vote for Jack Krushen - if only because his movie is so much better than those nominated here. As for Sal Mineo - he's the standout in that boring, un-epic (despite its scale and ambitions) movie, Exodus, and the only one with a remotely interesting character... but unfortunately Mister Tee is right (right, I mean, on Mineo's career, which except for these two justly nominated performances wasn't an especially distinguished one): I like Mineo, but voting for him twice just wouldn't be fair.
So no vote from me for the moment.