Android Saga and some of the Buu Saga. I really enjoyed watching the episodes that came right after the Cell Games ended and Mirai Trunks went back to his own timeline. Watching Gohan go to High School and become a Super Hero was something I found pretty funny. I really like the pairing Gohan x Videl so that's another reason I enjoyed the first few episodes before the Buu Saga.
Frieza saga hands down. Its the only saga where the battle takes place on a foreign planet, thus giving our heros real danger. I feel all the other big villains mimic frieza a bit with the transformations. Also, its the first appearance of a Super Saiyan so thats pretty cool! My least favorite would have to be the Buu Saga. I felt it went on for too long and I was disappointed in Gohans role durring this saga.