The envelope, please
A wonderful choice. To learn more, you can read the committee's summary of Ned's contributions.
Addendum: In the Nobel pool here in Cambridge, there were 209 entries. The favorites were Bengt Holmstrom (11.5%), No Correct Guess (10%), Robert Barro (10%), Oliver Hart (9%), Eugene Fama (7%), and Oliver Wlliamson (6%).
Update: I am told that one person out of 209 entries bet on Phelps.