Thanks to sgtdraino from http://www.losttv-forum.com for the following.
What do you the case could contain?
On Jay and Jack's recent 25-hour charity podcast, Jorge Garcia was asked about the guitar case Hurley had on 316, specifically if the guitar was Charlie's. Jorge Garcia responded by strongly implying that the guitar case does not contain a guitar. Hmmmmm! He said he is not allowed to say what is inside it, or who the contents are for.
Source: sgtdraino@LostTV-Forum