When a comic character moves into the "pubic domain" it means that its copyright has expired. It is amazing how many characters there are that anyone can use. Some are pretty cool and some are very weird. I found a great website that lists them all: The Fandom website.
Here are some of the more interesting and unusual characters I found.
There is, believe it or not, both a Fire Fiend and an Arson Fiend. I wonder if they are related. Arson Fiend fought (and lost to) Captain Marvel. Fire Fiend lived in Gotham City and battled (and certainly lost to) Mr. Scarlet.
There are also plenty of doctors, 57 to be exact. Above is a picture of Dr. Beerstein. It is unclear as to exactly what kind of doctor he is or whether he takes Medicare.
This is, after all, a toy blog so let's finish with Dollman. He's 6" tall, has the strength of a full size human, and rides around in a model airplane.