I love gn0sis's idea described in Using Unicode on E2 for adding the native name, in Unicode, to your writeups about foreign terms, concepts, people, etc.

Here are many important terms I have gathered in Japanese, all of them already noded or certainly nodeable.
They are listed first in English alphabetical order of the English word, English spelling, romaji, or English transliteration.
There are no doubt errors here since I don't speak Japanese, so please /msg me if you find an error, have an addition, or if you use one of these in a writeup of yours.

To use these, you can try just cutting and pasting into your writeup - this works for some browsers depending on the configuration. Otherwise, use your browser's "View Source" menu and cut and paste the HTML entities.

I've tried to list all the kanji variations I can find but I only list hiragana or katakana for those words which the Japanese themselves prefer to spell with them.

Japanese (日本語):

aikido (合気道, aikidō)
Ainu (アイヌ)
Arisugawa Juri (有栖川るい)
Asahi (朝日, アサヒ)
Battle of Sekigahara (?)
bonsai (盆栽, bōnsai)
chado (茶道, chadō)
chigiriki (千切木)
chokuto (直刀)
dan (’i)
dojo (道場, dojō)
fugu, globefish, blowfish, pufferfish, porcupine fish, sea hedgehog, swellfish (河豚, フグ)
futon (布団)
Gamera (ガメラ)
geisha (芸者)
Godzilla, Gojira (ゴジラ)
haiku (俳句)
Hamamatsu (浜松)
hara-kiri (腹切り)
hiragana (ひらがな)
Ikkyu (一休)
judo (柔道, 柔道, judō)
jujutsu, jiu-jitsu, jiu jitsu, jujitsu (柔術, jūjutsu)
kabuki (歌舞伎)
kaiju (?)
kamikaze (神風)
karate (空手道, 空手)
Kasato Maru (笠戸丸)
katakana (カタカナ)
kendo (剣道, kendō)
kimono (着物, kimōnō)
kinsoku (禁則)
Kirin (キリン)
koan (公案, kōan)
Kobe (神戸)
Kobe City (神戸市)
Kyoto (京都, Kyōto) - kanji already used by sekicho
Kyushu (九州, Kyūshū)
Meiji (明治)
mikado, The Mikado (帝)
miso soup, miso shiru (味噌汁)
Mothra (モスラ)
mushin (無心)
ninja (忍者)
Okonomiyaki (お好み焼き)
origami (折り紙, ōrigami)
Osaka (大阪, Ōsaka) - kanji already used by sekicho
otaku (?)
pachinko (パチンコ)
prefecture (県)
ramen (ラーメン, rāmen) already used by gn0sis
reiki (靈氣)
Rodan (ラドン)
romaji (ローマ字, rōmaji)
ronin (浪人, rōnin)
sake, saki (酒)
Sakurai's Object (桜井天体)
Samurai (侍)
sashimi (刺身, さしみ)
sencha (煎茶)
sensei (先生)
sentai (?)
seppuku (切腹)
shinto (神道, shintō)
shogun (将軍, shōgun)
sumo (相撲, sumoō)
sushi (鮨, 鮓, 寿司, すし)
Takatsuki Shiori (高槻 枝織)
tempura (天婦羅, 天麩羅)
teriyaki (照り焼き, てりやき)
Tochigi (栃木県)
tofu (豆腐)
tokusatsu (?)
Tokyo (東京, Tōkyō) - kanji already used by gn0sis
tsunami (津波)
Wasabi (山葵, わさび)
yakuza (やくざ)
Yukishige Tamura (田村幸誠)
zanshin (残心)
zen (禅)


Sources:
Google
Foreign language dictionaries at various Sydney libraries
Thanks to Gritchka for recommending splitting the larger entries out of my writeup for Using Unicode on E2.