Interesting and difficult question, but at least there are no wrong
answers. I'd probably have to say Pegasus, not for what's in it
telescopically, but just for it's simplicity, it's mythological subject,
and the fact that it sort of looks like the front half of a horse. It
also fills the nostalgia bill, as I can remember it being outlined on
the planetarium ceiling at the University of Nebraska when I was maybe 7
years old.
The years really do seem to go by faster
as you get older.

Best not to get me started on that one! When I was a kid, a year was a
significant portion of a lifetime. Now, I seem to have to figure out
efficient ways to circulate Christmas trees through the living room.
Marty