Oh wow there's so many! XD
I guess my first pick would have to be Midna, since she's my favorite Zelda character. I think she would be fun at the party and she would have a lot of funny and witty things to say.
Other than her, I guess I'd love to have Link, Zelda, Luigi, Ayane from DOA, and maybe a few of my favorite Harvest Moon characters like Skye and Julius. ^^