It's "In Park". (sorry, couldn't resist)
Link doesn't strike me as the kind of character who would have a last name. I'm not really sure if there is a perfect last name for him. To me, Link is fine as nothing more than "Link". Thinking about it, none of the other characters in the Zelda universe seem to have last names. I don't think last names are something Nintendo really thinks about when deciding names; they just focus on first names. I guess it's just going to have to be up to the player to decide.
odd topic.. maybe Link Anouma?? that sounds cool
Nah, Link's last name if he had one would be like Mario's which was Mario Mario. So Link Link is probably what it would be if he had one.
If it was medieval with today's terminology, it could be link bo$$. Really, link doesn't need a last name whatsoever. Just link. do you know anybody else named link?
EDIT: besides the goron one.