Give the option to assign a task without emailing the assignee(s).
With the addition of my nintex, some users are already asking for the option to just monitor their tasks in there on a daily basis rather than receive emails for each task.

If multiple users are assigned it would be good to chose who gets the email and who doesnt. This would be particularly useful to send a notification to a shared inbox and allow users of that inbox (also assignees) to complete the task as their users.