13. Ray Palmer
While Ray Palmer really made an impact when he left Arrow and headed over to Legends of Tomorrow in terms of being taken seriously (that was hard to say with a straight face) as a hero, he definitely did his part to shake things up for Oliver Queen and his team.
Not only did he end up taking over Queen Consolidated transforming it into Palmer Technologies, but his relationships with other members of Team Arrow also helped him to become more well-rounded as a character. In some ways, I think his relationships with both Cisco and Felicity are what helped them as characters grow, and watching the team work to save Ray from Damien Darhk was just the first step in having him work with Team Arrow to take on HIVE.
And even after leaving the city to board the Waverider, he continued to help the team whenever a crossover event would bring him back into the fold of his Arrow friends. Every time Ray met up with Oliver, Felicity, and the rest of the group, it was clear that he was just as much a member of the group as anyone else, even if he was no longer part of the team.
Maybe it is the fact that he understands being a vigilante or the fact that he has the tech knowledge to be support, but either way, Ray is always the guy you forget about as a hero, but suddenly he is there helping to save the day and he just makes it happen.