Macbeth is a perennial favourite because it is so taut. Similarly Much Ado always goes down well with all levels of ability. There is plenty of straightforward character based stuff which is accessible, and for the more capable social structures form a valuable way in to the play.Comic conventions and the role of laughter in Much Ado is also rewarding on a number of levels, which leads me to another choice - 12th Night. All abilities can appreciate and respond to the idea of the Lord of Misrule, and disguise is always a winner.