Seaman 2nd Class Warren P. Hickok of Michigan was reported missing after the surprise attack on Pearl Harbor, 64 years ago this month. His medical and dental records were recently matched to the remains of the unknown soldier identified as X-2, which had been interred in the National Memorial Ceremony of the Pacific after attempts at identification in the '40s were unsuccessful.
CNN's article says there are 88,000 unaccounted-for American service members from all conflicts, and the vast majority are from World War II.
http://www.cnn.com/2005/US/12/17/pearlharbor.remains/