6) Sandman
Upon hearing the term ‘Sandman,’ modern comic readers will no doubt first think of the protagonist of Neil Gaiman’s seminal comic series of the same name. However, there is a much older DC character who employed the alias first.
A classic pulp fiction creation, the vigilante Sandman (real name Wesley Dodds) clears up his city in a fedora and gas mask, using his trademark sleeping gas to put criminals out of action. He also has prophetic dreams of crimes which he then works to avert (a retcon revealed these were gifted him by Gaiman’s Sandman).
Also debuting in 1939, Sandman is a member of the Justice Society. So an introduction for him in Legends season 2 would be completely natural. In fact, like Ma Hunkel’s helmet, Dodds’ gasmask also resides on The Waverider. Given that, an appearance by Sandman in the Arrowverse is surely only a matter of time.