Darshan Sawardekar has released a very impressive looking plugin for Vim, appropriately titled WordPress.vim. If you use Vim as your editor/IDE, you should definitely check this out. The plugin includes support for an impressive array of features and other tools, including syntax highlighting (including highlighting deprecated functions), WP-CLI, autocompletion, the WpSeek API, and more.
The project also includes a CONTRIBUTING.md file on GitHub, a practice I'd like to see more projects in the WordPress community embrace. That will only serve to foster collaboration and improvement of the project. Darshan explicitly solicited contributions in his announcement post:
WordPress.vim needs the help of the WordPress community to keep improving. Please consider joining this effort by providing new snippets, new features or bug reports.
If you find that a feature is missing or find a big, please contact me or and add an issue to the issues tracker on GitHub.
I can't wait to use this plugin myself, and see where the project goes as more people get involved with it.