These are just some Japanese words that I know, some have to do with Pokémon/Team Rocket, some are just commonly used on my site or elsewhere. Please note that they may not be 100% accurate, or there could be other ways these words are used.
Pikachu: Sparkle Squeak (Pika=Sparkle, Chu=Squeak)
Ya na kanji: This Feels Bad (This is what Team Rocket says when they "blast off".)
Rocket Dan Yo Eian Ni: Let Rocket Gang Be Forever
Fushigi: Mysterious
Natsu: Summer
Umi: Ocean
Kawaii: Cute
Rakki: Lucky
Gomenesai: I'm Sorry (Or just 'gomen' for 'sorry')
Ecchi: Pervert (It is used in a lot of animes, seriously)
Hai: Yes (Although there are many ways of saying this)
Damé: No (Again, there are many ways of saying this)
Hyaku: Hurry
Konichiwa: Hello
-sama: someone you respect (Musashi-sama.)
-chan: someone you're close to (Kojiro-chan)
-kun: Child, usually disrespectful (Mondo-kun)
-baca: Idiot, used in a friendly way (Nyasu-baca)
Aho: Idiot, used in a rude way
Shiné (shee nay): Die
Koi: Boyfriend or Girlfriend
Karaoke: Tone Deaf (Betcha didn't know dat one! :P )