Golden Age (1938 - 1955)

Action Comics #1 

1st appearance of Superman. This is essentially the most expensive comic in the world and features the beginning of all superheroes. This comic has a massive value that can go from $500k to 3 million dollars. A book like this rarely goes up for sale, and when it does, it grabs the attention of all collectors.

Detective Comics #27

1st appearance of Batman. This comic is essentially a close 2nd behind Action Comics #1 and also fetches staggering numbers when sold. It can sell anywhere from 200k to 2 million dollars.