Corto Maltese is referenced in the Tim Burton film Batman (1989). Vicki Vale was well known for taking controversial photographs of the war torn island.
The Dark Knight Returns Part 2
Corto Maltese is featured in the animated adaptation of The Dark Knight Returns.
Corto Maltese is mentioned early in the series as one of Deadhsot's base of operations. In the season Three episode 3 (itself titled "Corto Maltese"), Oliver, Diggle and Roy travel to the island to find Thea Queen who had been training there with Merlyn. Mark Shaw, an ex-ARGUS operative was also there, trying to escape ARGUS buy selling info to terrorists.
The Suicide Squad
Most of the movie is set in Corto Maltese.