10. Calendar Man
Some characters should really just be featured in the background or as passing threats to Batman, and Calendar Man is one of them. As his name alludes to, Calendar Man is obsessed with calendars and dates. His major crimes often correlate with certain holidays or important dates throughout the year. That makes one of his largest assets his patience and ability to plan his crimes out. He waits all year for certain days to pull off his heists, never rushing or leaving anything to chance.
Not only is Julian Day (seriously) a great long-term strategist, he also has the inventing chops to develop some heavy-duty weaponry. He’s been shown alternately as a clownish character — a Hannibal Lecter-esque serial killer and a master manipulator. All three would work well on the big screen so I really hope he gets something soon!