A towel I was given as a gift by a new neighbor when he introduced himself.
In Japan, there is a custom in which neighbors go door-to-door and introduce themselves when they first move into an apartment building. While this custom is not followed by every single Japanese person, it is done about 80% of the time in my experience. Usually, the new neighbor introduces himself or herself with some sort of small gift, such as a towel, soap, or food. Of course, when one moves, one is expected to carry out this ritual as well, even if one is a foreigner (but you are forgiven if you're not aware of the custom).
This is a nice custom which helps you recognize the new neighbors in your building and increases the chances of a friendly relationship with them and I will miss it.