i wan't!
<grammar nazi>
It's actually "want". The apostrophe has two uses in English:
1) Possessive case. "This is KeFF's Gameboy" and so on.
2) When some letters are omitted.
Don't = do not. Can't = can not. It's = it is.
Want on the other hand is a verb on its own and not a short version of something else. (That's why you "he wants" but not "he don'ts".)
</grammar nazi>