I love Popclip. The extensions that I have added:

- spelling

- paste and match style

- various capitalization scheme (change to title case, change to sentence case, all caps, all small, etc.)

- Dictionary look up

- word count/character count

- make bullet list

- sort list alphabeticall

- copy as markdown

- open in textedit

- create todoist task

- create fantastical calendar entry

There are others I thought I would use a lot like look up on Google or look up on Wikipedia, but for some reason I rarely remember those. Todoist and Fantastical are immensely helpful for me, as well as spelling and dictionary lookup