In Japanese this is pronounced: Donkiho-te, or just Donki for short. Donki is a discount store where you'll find random, funny, and really useful things to bring back home with you. You can shop tax-free if you show your foreign passport to prove that you are a tourist!
Japanese health products and supplements are really popular! A lot of Japanese products focus on anti-aging, anti-oxidants and immune support, so people even in the U.S. order them online. At DonQui you can buy them tax-free and at discounted prices.
Lunch boxes (obento), and thermoses are also very popular with visitors to Japan. They are made well in Japan because they are used so often by Japanese, and they make great souvenirs for to use at home or great gifts.
Cooking ware, especially ceramic knives, are also really popular. If you're planning on bringing these back, though, check with your airline about their regulations and restrictions.