summer bbq party

so i'm having a summer bbq party.  and there is to be a rib cookoff.  and i was surfing around some hostessing blogs and now i think it would be fun to have a guess the secret ingredient in the margarita game.  i think i just love games.  anyone have any good margarita recipes?  in case some sneaky participants actually read this blog, i'll post the marg recipes later that i end up using.