Okay, so browsing one of my favorite catalogs, Uncommon Goods, I saw something that IMMEDIATELY made me think "wedding guest book!!" I think it'd be so fun and unique - and aren't we all looking for ways to make our weddings fun and unique? :) I loved my guest book, but I really wish I'd seen this first!
It's a cardboard frame with a honeycomb inset into which people can insert their wishes. It comes with 500 multi-color slips of paper, but how cool would it be if you cut your own out of beautifully patterned paper, or paper that matched your wedding colors? The frame itself can also be painted or decorated or covered in fabric to personalize it. And needless to say, it'd be a blast photographing it. :)
You can buy it here!