Dalek Sec

Dalek Sec is a visionary. He dreams of a new Dalek race, existing outside the shell. So he transforms himself into a Hybrid, able to walk without his Dalek Casing but also vulnerable to attack. His other Daleks dont like this too much, and they end up betraying him. He does lead them to victory against the Cybermen, however, with his awesome verbal whipping of their leader, as shown in the clip below.

He leads the Cult of Skaro.

Despite being a Dalek he wanted to change how Daleks worked, thus being the only Dalek to think so. He combined himself with a Humans to become a Hybrid, and planned for all Daleks to do the same. However, Dalek Caan didn't much like the idea of getting legs so he took over control of the Cult. Dalek Sec was 'accidently' killed by Dalek Thay later on, but really he got in front of Dalek Thay's gun to save the Doctor's life. Soon after, Sec's Dalek-Humans turned on their masters and destroyed Daleks Thay and Jast, forcing Caan to flee.

Youtube Clip
http://www.youtube.com/watch?NR=1&v=kBSOhODoch0&feature=endscreen