Uji-kintoki is best in summer!
Japanese shaved ice is called kakigori. There are a variety of flavors, and a traditional kind is Uji-kintoki which is flavored with green tea syrup and anko (sweet azuki beans).
Kakigori is available in a wide range of quality: ranging from average quality found at the local grocery, to high quality from specialty shops such as famous green tea restaurants. Try it at one of the special restaurants once - they shaved ice is airy and fine. Taste very different. Sweetened condensed milk is often poured, which is my favorite!