My husband and I gave out small silver-plated photo frames.
If you've got a break between the wedding and reception (as we did, for formal photos at the church and a local scenic spot), have some stalwart soul who's handy with a digital camera take a photo of the bride and groom at some point during the ceremony. Make sure he/she gets you to approve the photo. Then have someone hasten to a quick-print place and have lots of wee photos printed, sized to fit the frames. Have some volunteers ready to insert photos into frames and frames into gift boxes. When your guests get to the reception, on their tables will be the very first print of the new Mr./Mrs., in a keepsake frame. Of course, they'll all treasure it forever.
It may seem labor-intensive, but if you've got enough helpers it should go smoothly. It would help, too, if in advance you go to a quick-print place and enlist their aid so they're prepared to turn things around fast.