Southern 2nd person plural pronoun. Most concise and easily distinguished. Despite the assurance of some emails that have been passing around, "y'all" is plural. Only an absolute idiot would use it as a singular pronoun.
contraction for you all. Despite what some think, it is not only used by hicks and the uneducated. People from all walks of life, traditionally the southern states use it.
The best way to address two or more people. Better than: you guys, youse guys, and you all! Yes, I live in Southern Alabama, and yes, I attended Harvard!