よ: The particle that never needs translation
(disclaimer: may be nonsense)
It's occured to me that the best (or at least the most awesome) way to translate よ is always Yo!
Even the famous WWWJDIC agrees: "(int) (4) yo!"
Proof, from the WWWJDIC example sentences for よ:
'Number-withheld' calls are scary, it's best not to answer them, Yo!
That is a criminal offense and you will surely be punished, Yo!
I challenge anyone to come up with a sentence with the よ particle where the english word "Yo", is not awesome.