it's a hard one to answer - I suppose one thing I love is that moment of cognition(? I think that's the right word) that can come pretty suddenly.
a good example is the last time I was looking at Jupiter - the seeing was excellent, and my scope was properly collimated (so all the stars were aligned
) and it was like looking out of a portal. I've never felt so physically and imaginatively transported - stepping away from the eyepiece was jarring. I felt like I had actually
seen Jupiter, as opposed to merely viewed it. (and the rational side of me says "what a load of wank")
I had a similar experience looking at the area around markarian's chain - mind=blown.