Sagittarius A* come on it’s the biggest black hole in the galaxy. If it’s eating something it’s going be amazing to watch.
If not that then any planet on the outer edge of the galaxy up above the ecliptic where you could see the whole galaxy at once in the night sky.

Maybe a comet? That video of Comet 67P from the Rosetta mission looked really cool.

With some other planets and celestial bodies, the photos are often edited or in a spectrum that we can't see with our eyes. So I'm not sure which ones will be nice to experience otherwise. If I had to pick a planet, I'd go with something with rings so I could fly through them

Uranus

One of TRAPPIST-1's planets. Just long found that system in particular interesting.

I would go in a yellow submarine under Europa with the beetles.

Personally, I would really love to go to Titan. The methane oceans and thick atmosphere seem really interesting!

But many of the other bodies just in our Solar System are super cool too. Venus is a hot destination, I would love to visit Ceres, the queen of the asteroids, and many of the icy moons would be fun to explore too (think Europa, Callisto, Ganymede, Enceladus, Titania, Triton...)

Risa

I think a quasar, would probably be one of the most dramatic things to look at.

The andromeda galaxy would be cool.

I wanna see what's beyond the event horizon of a black hole.

Just for sightseeing? I mean without the capability of doing some tests/gathering samples? None then. Those planets are dead and boring aesthetically. We have visually similar shit on Earth somewhere in deserts/mountains/poles.