I used a bible and a wall calendar. We got a journal bible (kjv) and asked guests to find encouraging scriptures that they want to highlight for us to read and apply to our marriage then sign or write anything over the notes section. The calendar (purchased from Vista Print) we used 13 pictures from our engagement shoot for the cover and each month then asked guests to find their birthday and anniversary and sign in that slot.
We are getting married on a ski mountain and having the reception at the lodge. FH and I snowboard and we getting a wooden snowboard with last name engraved in the middle for guests to sign off Etsy. Once I saw it I know I would want this to display at home post wedding.