I'll be that guy...
Anything really useful in that price range I would already have, don't even try.
I'd rather it was spent on a couple of good steaks, beer and a couple of hours of frank talk about how my son is doing with his life.
Better than that would be anything my son spent some time making or restoring. Whether or not it's useful isn't the point. The point is that he took the time out of his busy life to do it for me. As an example, go to antique store, garage sale, etc and find something and restore it. Or something broken he's kept around because it's sentimental and fix it for him.
One year for my son's birthday I fixed an old flashlight his grandfather gave him and updated it to use an led bulb. It now works and makes useful light. He now remembers us both when he sees it.