2

Jack tells Sawyer that without the antibiotics, he'll feel fine for 2 days, but then 2 days after his arm begins to itch, he'll beg Jack to cut it off

To access the safety deposit box, one needs 2 keys.

900

Shannon says that Laurent's son watched the animated fish movie (Finding Nemo) "900 times."

5025

The toy plane Kate retrieves from the Halliburton box (and presumably from safety deposit box 815) is a model DC3, manufactured after 1935. The number on the toy plane wing is 5025.