The two parts that always stick out in my memory are:
Goku vs. Mercenary Tao
and
Gohan vs. Cell
Yes, Goku going SS against Freiza is a great moment, but you can't deny Cell's general awesomeness or the epic [http://www.youtube.com/watch?v=9-xAViaWJvI] music [http://www.youtube.com/watch?v=aUCSNrACjdE].
Goku vs. Mercenary Tao
and
Gohan vs. Cell
Yes, Goku going SS against Freiza is a great moment, but you can't deny Cell's general awesomeness or the epic [http://www.youtube.com/watch?v=9-xAViaWJvI] music [http://www.youtube.com/watch?v=aUCSNrACjdE].