6. Nightwing
Nightwing has long been a fan favorite of the DC universe. Nightwing is the alter-ego of Batman's first sidekick, Dick Grayson. Dick's all grown up now and patrols the neighboring town of Bludhaven, where he faces off against police corruption and organized crime. The character has made several appearances in various DC animated TV shows, including The New Batman Adventures, Batman Beyond, Justice League Unlimited, Teen Titans, Batman: The Brave and the Bold, and Batman the Animated Series; and has appeared in several video games as well. Nightwing almost received his own animated feature a few years ago when DC planned on adapting The Judas Contract, a Teen Titans story featuring Robin's transformation, but the project was put on hold and ultimately cancelled. Nightwing has only grown more popular since then, and has been one of the characters fans are adamantly hoping will appear on Arrow somewhere down the line. Since DC loves adapting stories based around Batman, perhaps one featuring his fellow sidekick could still be a possibility.