I bought my husband a silver pocket (wallet) piece from James Avery Craftsman for the birth of both of our sons. I engraved our son's name on the back along with his birth date. When they turn 18, he's going to give each his to keep. Both are different, one says "Fear not for I am with you" and the other says "Trust in the Lord........and he shall direct your path."
There are a lot of nice little pieces at James Avery, but if you want something non-religious, what about setting him and your baby up for a black and white candid photo session? Our's are our favorite thing in the house. We used Paul Dyer. He's a master at natural light and BW. He did our wedding, engagement, pregnancy, baby and family shots. He's amazing. Mmmmm.....I think his number is ###-###-####, and his site is www.dyersphoto.com. Tell him J. Wylie referred you. I think he's working in McKinney now. He was in Addison.
Hope you find something perfect!
Oh, one other rather random thing if he's more contemporary. We just wrote an article on DNA and fingerprint art. you get a kit and can send in a swab from both, then you pick a color scheme, then they produce a piece of art for the wall with both of their DNA. Weird, I know, but at least he'll be the only one in town with one! www.dna11.com