9. Hook
"From up here it almost looks like that guy with a hook for a hand has a gun." Are among the last thoughts that trapeze artist, Boston Brand, has before he falls to his demise. Brand himself would come back as Deadman, a hero with the ability to possess other characters. His death would echo the death of Dick Grayson's (The first Robin) parents, a sentiment the two would share together in the comics. The act of killing this acrobat was Hook's (Real name: Matson) initiation into The League of Assassins. Obviously I would doubt the series would show his affiliation to The League of Assassins, but I'd love if this were an inter-network companion to Arrow. Arrow itself has made use of League members, and will be adding more with its second season as Bronze Tiger makes his debut. His importance in the DC universe isn't my reasoning for this character needing to be in the series though. My reasoning is more basic... We're never getting Robin, but the death of the Grayson's is an integral part of DC lore. Using hook would be able to show the circus, the death, and maybe even the Grayson parents... if not a mention of a young Dick.
Ideal Casting: Come on... Jeffrey Donovan. Does he not look like Michael Westen with a hook? Besides, who wouldn't want to see Donovan back on tv and kicking some butt now that Burn Notice has ended?