GeneratePlugins
GeneratePlugins is a free online service that lets you generate very quickly a fully OOP standardised Word/ClassicPress plugin.
You are able to manipulate all details from plugin name to tags, requirements and variable names.
The service then generates and downloads a Plugin Boilerplate crafted with fully WP Coding Standards and general best practice OOP standards which you can use to build on top.
It even has example code in the source for filters, actions and shortcodes, public and admin display.
generateplugins.com
WPPB
This is another Plugins generator, however less sophisticated than the above, and the codebase is less evolved, but it is based on the same principles. Its codebase is not anymore actively maintained, as opposed to the GeneratePlugins service, however, still pretty much solid.