Emphatic particles are tacked on the end of sentences in Japanese to express nuances and social aspects of communication. They're difficult but if you can learn how to use them, your casual Japanese will sound much more natural.
Ne is probably the most common. It was definitely the one I noticed first. Ne is used to seek agreement or confirmation, or to try to get a point across. It's also used to ask a question.
'It's cold, isn't it?'
Sore wa chotto muzukashii desu ne.
'That's a little difficult, y'know?' (actually this is a way of saying 'no')
Kirei da ne
'Beautiful, isn't it?'
Yo relays new information or adds emphasis, something like an exclamation mark.
Kare wa mou kokosei desu yo
'He's already a high school student.'
Wakatte iru yo
'I know already.'
Ki ni sunna yo
'Don't worry about it'
Yo ne can be a more emphatic way of using ne.
Kono bando ii yo ne
'This band is good, huh?'
Sono seta niau yo ne
'That sweater really suits you, doesn't it?'
It can also be used to check for confirmation.
Kino denwa shita yo ne?
'You called me yesterday, right?'
Ore, isogashii nda yo ne?!
'Can't you see that I'm busy?!'
No is used mostly by women and, like nanda or nda for men, can be used when explaining something.
Kono yubiwa hoshii no
'I want this ring.'
Ima isogashii no!
'I'm busy right now!' (response to somebody asking her to do something)
It's also used for emphasis.
Ano hito kimochi warui no
'That guy's a creep.'
Yamete hoshii no
'I really want you to stop that.'
Na is used to express strong emotion or to express a desire for something. As a strong emotion, I mostly hear it used by men. To express desire, it's used by men and women.
'Ano hito sugoi na'
That guy/girl is amazing.
Supein ikeru to ii na
'I wish I could go to Spain.'
Kono heya kitanai na
'This room is dirty.'
Na can also be used as a negative command.
'Sonna koto iu na!'
Don't say that!
'Kocchi minna yo'
Don't look at me
Ze and zo
Ze and zo are emphatics that are usually used by men.
Deizuniirando iku zo!
'We're goin' to Disneyland!'
'I'm gonna cry'
Ze is also used to add emphasis.
Kono raamen umai ze
'This ramen is tasty'
Wa is an emphatic used by mostly by women. It's considered effeminate.
Read more: Gender differences in modern Japanese
Sawaranaide hoshii wa
'I really don't want you to touch me.'
Men sometimes use wa at the end of sentences to indicate some future action.
Ore mo biiru kau wa
'I'm gonna buy a beer too.'
Okutte ageru wa
'I'll give you a ride.'
Finally, there's sa, a particle that's used to death in Chiba where I live. This isn't so much an emphatic as it's a filler, like the incessant 'like' or 'y'know' that some English speakers use.
Ii nda kedo sa…
'It's alright but…'
It's tough to use emphatic particles correctly, but listen to enough natural Japanese and you'll get the hang of it.