I always thought he was underrated in this regard. I like Goku's intense rivalry with Vegeta, but I also like Piccolo's friendly rivalry with Goku in the late Freeza Saga and the Android Saga/Early Cell Saga, when he helps Goku stall against Freeza, and when he trains with Goku and Gohan in preparation for the Androids. What do you guys think about Goku's rivalry with Piccolo?