Arbutus or fruit of the strawberry tree. In Palaiós Panteleimónas, on the slopes of Mount Olympus, they make the fruit into tsípouro; you may also see arbutus honey, μέλι κουμαριάς (méli koumariás).
On Kythera, they make a bite-sized sweet from the fruit called koúmara κούμαρα
Image by Dana Facaros