Only watched a few episodes of DB but the moments of DBZ for me are:
Goku's Super Saiyan speech to Frieza
Gohan going SS2
Goku's Sacrifice in Cell Games (the best)
Gohan 1-handed Kamehameha
Goku going Super Saiyan 3
Mystic Gohan fighting Super Buu
Goku's Super Saiyan speech to Frieza
Gohan going SS2
Goku's Sacrifice in Cell Games (the best)
Gohan 1-handed Kamehameha
Goku going Super Saiyan 3
Mystic Gohan fighting Super Buu