Cacher is the code snippet organizer for pro developers

Source: http://www.unchi.co.uk/2012/02/20/forcing-paste-clean-up-in-tinymce-all-installations-and-modx-evolution/

paste_auto_cleanup_on_paste : true,
paste_remove_styles: true,
paste_remove_styles_if_webkit: true,
paste_strip_class_attributes: true,

Adding lists to the plugin list in settings is also a good idea.

The plugin prevents tinyMCE from adding spans to list items.
https://tracker.moodle.org/browse/MDL-38329

Also, without the lists plugin tinymce cannot handle nested lists. Stupid!

I have still problems with styles added to links... :(