My favorite character is Piccolo. I am a hardcore fan of Dragon Ball, I have been a fan for all of my life. I watched Dragon Ball Z from a young age, as well as the original Dragon Ball and GT. I was hyped for Dragon Ball Super when it first came out as well.
My favorite technique in the Dragon Ball series would have to be Krillin's Destructo Disc. No matter how strong the user is, the attack can cut through anything essentially. Krillin, while much weaker, could have killed Frieza with it. It would have done no good against Cell though since Cell could regenerate and he personally knew Krillin's Destructo Disc. Krillin first uses Destructo Disc in the Saiyan Saga against Nappa, so I guess he invented it while training with his friends at the lookout. Frieza kind of copies the Destructo Disc and other characters use it too since it is such a cool technique.
I used to say Tien was my favorite Human character but it turns out he isn't exactly Human. He is a Human hybrid though. This page says it all.