What are some good Japanese souvenirs?

Snack foods!

We have very unique selections of junk foods, but I believe they are not as bad as foreign junk foods. Some have very pretty shapes and others have very unique tastes. You should check the names of the products, because there are some very funny English names. Also, we have a lot of "green tea" flavored sweets, which are very Japanese. "Kit cut" has even Japanese original flavor. However, do not buy simply chocolate covered “Pocky”, it is all over the world now. Many foreigners I know say they like chocolate from "Meiji"
Visit a supermarket, or a convenience store. You will find a lot of new things.

You can visit local kimono shop, you'll find not only kimono,

but also traditional Japanese style Accessories which you'll never find anywhere else.
Such as hair accessories, purses, sandals.

Also, I'd like to recommend Japanese stationery.
You can find something rare.. Japanese traditional (such as cherry blossom pattern) style, cute stuff, unbelievably functional things there.
How about writing letters to your friends from Japan using Japanese style letter pad and post stamp?

If you have only small space in your baggage, Japanese wrapping cloth (Furoshiki) may be a choice.

Japanese foldable fan will be good. This is a Japanese hand-operated fan. Because there are a lot of designs, please buy it which a friend seems to like.

https://en.wikipedia.org/wiki/Hand_fan#Japanese_ …

Food Replica Samples / Fake Plastic Food

http://fake-food.net/

Kabuki-designfacepack
http://isshin-do.co.jp/designfacepack.html

Sushi USB Flash Drives
https://insight.japantoday.com/get-souvenirs-jap …

Ask your friends. No one knows your friends' favorites on this site.

Some tourist prefer to have foods (Be careful for your country's rule of Customs),
electronic goods, traditional goods, and so on.

For example, my Taiwanese friends asked me to buy medicines and watches of "Wave Ceptor".
My French friend asked me to buy a LCD protection film for his mobile phone.
My Indonesian friend asked me to buy a Japanese-Japanese dictionary.