I used to watch every day after soon when it wasn't on the Saturday night line up. Then I was so stroked every Saturday night. I can't really pick a favorite since I loved so much of them.
Gundam Wing, Rurouni Kenshin, Yu Yu Hakusho, Dragon Ball, Dragon Ball Z, Rave Master, Ronin Warriors, G Gundam, Transformers Armada, Beast Wars: Transformers, Zatch Bell, Zoids Chaotic and New, Justice League. <3 almost all Toonami programing. I'd say Naruto, but I really don't care for the anime anymore all about the manga.
Heck I could even watch their promos for hours(Peter Cullen <3), just good all around stuff.