Dexter's Journey. A children's story about an heroic rubber duck that travels the world.
You DO hear a lot of dogs "Dexter! Dexter!"
Also, as per pp, a big estate agent chain here in London which is not always well thought of. Not relevant if you live further afield though.
BUT... I think it is a very cute name for a boy. Can you imagine it for an adult? If yes, go for it.