PICCOLO

Piccolo plays a substantial role in Dragon Ball Z. He's from the planet Namek, where the dragon balls were created. If Piccolo would be killed then his other half, Kami, and the dragon balls would disappear. So, it is very important that Piccolo survives a battle to make any wishes necessary for revival.
Piccolo's personality is great. His relationship with each character is unique. He cares very much for Gohan ever since he's trained him. Piccolo could be considered as Gohan's other father because he's there for Gohan when Goku isn't. He'll defend and even sacrifice himself for Gohan. Part of the reason why I think he'll defend Gohan with his life is because when Piccolo does, Goku isn't around, so if Gohan were to be killed in front of Piccolo, he would have to answer to Goku, and Piccolo knows that Goku is stronger than himself so Piccolo wouldn't want to have to deal with Goku's anger!!! Get where I'm coming from? And Piccolo has respect for Goku, he admits that Goku has overcome his strength and is a better fighter. Krillin and Piccolo, well eh, Krillin seems to have a little fear of Piccolo since Dragon Ball. Piccolo and Vegeta's relationship is great! It's two, bad, evil, characters against one another!
Although Piccolo may seem to be evil and mean, he's really a good guy!