One of the most useful additions to Mac OS X has been the share button in Safari. A common thing is to send relevant links via email and the easy efficiency the share button introduced is great.
If you happen to have more than one email account though, this becomes more complicated. If you use Outlook for work, and Mail for personal communications this creates a problem when attempting to share from the non default email client. A clever trick would be to allow the selection of another client via a modifier click, for example an alt-click or shift-click could open the share menu with the other email client selected. Better yet, allow a user to decide what apps or services to add to their share sheet. (Bonus points for allowing the format of the share be edited like an email signature.)
While on the topic of Safari, here is another one on the wish list: paste and go. Seriously, if you’re pasting a URL into the address bar shouldn’t Safari have the option to efficiently go to that page without extra inputs? How often don’t you want to paste and go? Ideally this would be implemented as a right-click menu item and a modified keyboard shortcut (alt-cmd-v perhaps?)
Streamlining repetitive tasks brings a sense of delight to the user, as they realize that the engineer on the other end of the code is considering how to best optimize the experience. Adding these things suggestions would demonstrate the consideration of what could make Safari even better.