Complimentary ID

From Zelda Wiki.org

The Complimentary ID is earned by buying thirty items from Beedle in The Wind Waker, thereby accumulating thirty points (see Silver Membership). It has no material use, but presenting it to Beedle leads to a somewhat humorous scene in which he does little more than compliment you on your continued shopping at his store.

In Phantom Hourglass, Link is given a Compliment Card upon obtaining a Gold Membership. It serves the same function as the Complimentary ID.