If you avoided the 'baby' type presents, you could go for a longer term gift with something from Tiffanys like a keyring ? It would be something the boy could use when much older and you'd get the fab turquise box / white ribbon which is pretty memorable.
For my god-daughter I got her an antique rattle, she couldn't play with it but they can't play with many of the christening gifts which is why I would be inclined to get something more useful ans special for the long term