These should be used with something like tampermonkey
Allows you to see the hidden text when clicking the "ALT TEXT" button on the webcomic site Oglaf
Uses the official API so it's faster and better than the older versions of this but it's bare bones so no options (yet)
Lets you curate your blogpack lists on tumblr a hidden feature that creates custom feeds based on a comma separated list of usernames.
It's functional but it is bare bones.
These are not to be used at this point