Timon of Athens, with line numbers by William Shakespeare

Sometimes classified as tragedy, sometimes as comedy, and sometimes as problem play. According to Wikipedia: The Life of Timon of Athens is a play by William Shakespeare about the legendary Athenian misanthrope Timon (and probably influenced by the philosopher of the same name, as well), generally regarded as one of his most obscure and difficult works. Originally grouped with the tragedies, it is generally considered such, but some scholars group it with the problem plays.