Most people who watch anime and read manga are also interested in the language the anime or manga was written in or spoken in (in the original). This language is, obviously, Japanese. Below is a list of vocabulary and also some phrases you might hear while watching the anime, or read while reading the manga. This is by no means a complete list of what I know, but it's a start. If you want a good webpage to help you start speaking japanese, try maktos.com. It's a pretty good site ^^ and it helps a lot. However, the best way to learn the language if you are interested is by taking a class. There aren't a lot of colleges or universities that allow it, and thankfully I attend a college that allows me to take the language as a course.

baka - idiot
oyasumi nasai - good night
kuso - damn (also translated as "shit!" and "crap!", etc.)
konnichi wa - hello
moshi moshi - hello (on the telephone)
nani - what
naze - why
mamono - devil
kurai - dark
hidoi - terrible
sugoi - wow
yatta - I did it!
aishiteru - I love you
aniki - brother (older)
jigoku - hell
minna - everyone
namida - tear
konya - tonight
daisuki - I like you / I love you
koibito - lover
koi - love, like (or carp :p)
shinu - to die
yami - darkness
tenshi - angel
saigo - last
okaeri - welcome (back)
tadaima - I'm back! (home)
uso - lie (as in, not the truth)
uta - song
doko - where
dame (na) - bad, wrong; useless, impossible; necessary (ikanakutewa dame = necessary to go)

1 ichi, hitotsu
2 ni, futatsu
3 san, mittsu
4 shi, yottsu
5 go, ikutsu
6 roku - muttsu
7 shichi (also, nanatsu or nana)
8 hachi - yattsu
9 kyu - kokonotsu
10 ju - tou