I have operated public observing nights at various universities for eight or ten years. These are the objects that have stood out for me.
Saturn and Jupiter are the "stars" of the night sky. Bar none. Spec. Tac. U. Lar. If you can look at Saturn with nothing between it and your eye besides a few panes of glass, and see it hanging in the sky in all its glory, and NOT want to be an astronomer, there is something deeply wrong with you. You can see both the Galilean moons (good opportunity to give an historical lecture, if you're a yarn-spinner) and the shadows of the Galilean moons pass across the surface of the planet. Some of them are fast enough to change noticeably between the beginning and end of an observing night.
The other inner planets, if up. Lots to talk about with them.
The Moon itself is a "destination", not just an obstacle to observing.
The binary star Albireo (the "head" of Cygnus the Swan) is fairly spectacular if you have developed a sense of what's "normal", because it is one of very few objects in the sky that's multiple colors- i.e., Jupiter is brownish, Mars is red, Saturn yellow, most other things white, but Albireo is bright enough that its member stars are distinctly blue and yellow.
Mizar and Alcor (the middle stars of the Big Dipper's handle) are conceptually neat, if visually dull. Mizar and Alcor are a visual binary, while with a backyard grade telescope Mizar resolves into a binary pair (telescopic binary), and with a spectrograph, you can resolve each of those into pairs of stars themselves (spectroscopic binary). So, in one telescopic view, you get all three kinds of binary stars.
The Christmas Tree Cluster (near a foot of Gemini) really, really looks like one (with an 8-inch refractor, in a fairly light-polluted area), complete with Christmas lights, a star at the top, a trunk, and a smattering of presents underneath.
The Beehive Cluster is pretty spectacular as far as open clusters go. Unusually uniform brightness gives it a real appearance of bees.
If you're ready to propose to your girlfriend, it would be hard to beat the Ring Nebula.
The Messier globular cluster M13 in Hercules is really easy to find. It lies right along one of the lines between the four trapezoid stars.
Orion Nebula. Talk about the Trapezium and star formation. Cool stuff
Pleiades- Lessons in multiculturalism (Different cultures call it different things), consumerism (Subaru logo), and optometry (How many stars can you see? Good vision, 7, 20-10 vision with experience in night sky observation, 14+)
Uranus- Giggles, and then its historical background.
Constellations and asterisms are a lot of fun too, because the audience can "take them home," that is, enjoy them again on a different night when they aren't being treated to a star party.
Get a green laser pointer. Absolutely indispensable, and also has a HUGE "wow" factor.
EDIT: Oh, and the Andromeda galaxy. The observatory where I did most of my observing was too badly light-polluted to see it very well, but if it's dark enough, it's the farthest object any human being in history has ever seen with his own two eyes. The Double cluster in Perseus is pretty impressive in binoculars, but it's so big you can't really appreciate it in a telescope. It's a good object for a n008 to try for her first solo "spot."
EDIT: This is a fairly comprehensive list, including planets, double stars, open clusters, a globular cluster, a galaxy, and nebulae. That's close to a Noah's Ark of everything you can possibly see with a backyard telescope, if you add transients like comets and satellites, and maybe a few other odds and ends like Ceres (though I've never attempted that myself. Is it actually pragmatically visible?)