Writer's Block: The Best Invention
Guttenberg's Printing Press. While someone else probably would have come up with something like it eventually, this invention, being the first of its kind, brought the written word to a great deal more people than ever before. Previously block printing was available, but as any one block could only be used once, books were very valuable because of the time, effort, and money needed to produce them, not to mention the supplies and the skill of those carving the blocks to prepare them for inking.