Finding the perfect gift for a couple celebrating their 50th wedding anniversary isn't so easy. After all, by their age they have probably accumulated most material things that they have needed or wanted and they might very well be in a 'simplifying' their life-stage. But that doesn't mean you can't find the perfect 50th Anniversary gift that will be meaningful and appreciated.
Give a Memory: Perhaps you have some terrific pictures taken of the couple 'through the years'. Have copies made of the pictures and then frame them as a collage. Or simply take one and frame it. If you have memories associated with when the picture(s) was taken attach a short note describing it.
Give them the 'headlines' gift from the day they were married or for the date they are celebrating their 50th anniversary. The web is a terrific place to find sources to purchase a front page from the day they were married (in your search bar, type "day born headlines") or to have a personalized headline made (this time type "Personalized Headlines").
Give an Experience: Think of the couple's likes and interests and give them something related to it. Perhaps they love Italian food. Then give them a gift certificate to their favorite Italian restaurant or a 'homemade' gift certificate for an Italian dinner at your house? Do they go to movies, plays, the symphony, etc? If so, give them either gift certificates for a movie theater or tickets for a play or symphony (make sure they don't have season tickets, though, to the venue)
Give a Group Gift: Perhaps there is something that the couple really, really wants and it is out of their financial reach and certainly out of the financial reach for one guest member alone. For example, they would love a weekend in Chicago or perhaps a newer TV/DVD player. If you have a large enough guest list you may ask if, instead of individual gifts, would the guest(s) be interested in donating X amount towards the big purchase. Make sure that it is not an unreasonably high amount so that no one will feel put on the spite. Also make it clear that they, in no way, need to feel that have to go in on a group gift.