Besides the Sun, Moon, Mars, Saturn and Jupiter the only 2 things my wife has found very interesting to observe with me was the ET cluster because it was easy to tell that it acually looks like ET and Albireo because you can really see the color difference between the 2 stars. Most people have no idea that stars are different colors and this can be quite a revelation to some. If you have super dark skies then some of the brighter dso's (m31, m13, etc) might impress your lady as well. Another cool/romantic thing to do is suggest going for a walk when you know there will be an iridium flare or that the ISS is going to pass over head.
For romance imho *nothing* beats the summer Perseid meteor shower. It's warm, the crickets are chirping, and the show is bright and impressive. Just lay out a blanket and lie down together to watch. Nothing to explain, nothing to squint at. Just a nice, quiet romantic time together and one of the most impressive and reliable astronomy shows there is. Astronomer's version of "long walks by the beach", LOL!
Tried this for a late-night date about 11 years ago. We've been married 8 years now.
Kemble's Cascade, which is located between Polaris and Mirphak in Perseus. Use three 3rd mag stars as pointers. It's a long line of 5th mag stars ending in an open cluster, an NGC object for which I don't recall the number right now. Kemble's Cascade looks like a diamond necklace ending in a diamond pendant. You want to be romantic and impress the lady, give her this one...