Hi V.,
Not sure what your son's interests might be, or what his maturity level is, but for my 7 yr old son who is a Cub Scout, we got him a Swiss Army knife. He is so proud to have it (and of COURSE he is not allowed to keep it in his room, or have access to it unsupervised) BUT just the fact of owning one that's his very own,and just like Dad's and Grandpa's :) makes him very proud. He likes to show it to everyone (again, under supervision) and we will let him use it on camping trips, and for occasional tasks around the house. And it's something he can keep for a lifetime :)
If he likes gardening, perhaps some of his very own gardening tools.
If he likes art, then maybe some really nice or special art supplies.
Hope this helps. Good luck and Happy Bday to your sweet boy!