1. Watching, awestruck, the absolutely amazing Leonids Meteor Shower of 1966. They fell like rain! (it's what initially got me hooked on Astronomy)
2. Aurora Australis as a kid and teenager in Sydney
3. Comet Halley in 1986
4. SuperNova 1987A
5. Seeing the rings of Saturn for the 1st time (in my home-made scope) 1991
6. Finding my first distant faint Galaxy cluster (Fornax Cluster) in my 12" Dob 2005
7. Comet McNaught 2007
and Comet Lovejoy (gotta give Terry a rap
)
Oh, and being the 1st person to discover a major SEB Band alteration on Jupiter in 1989, and recording it in sketches and handwritten data, and published in the Ballarat Astronomical Journal, but not recognised or credited as being 1st.
2 Japanese Astronomers were given credit when discovering it days later.