This resignation letter is perfect for when a departing employee is allowed to name the person who will replace them.
January 25, 2018
Dear (Employer Name),
Thank you for the wonderful opportunity to work here at (Company) for so long and to be able to accomplish (achievements). I am writing now with great regret to submit my formal resignation, as we previously discussed. My last day will be (date).
As it is my right and pleasure to do so, I would like to notify you that I will be appointing (Name) as my successor. (Name) has already shown tremendous talent, perseverance, knowledge and skill in (areas) and in (actions). I will transfer all of my (files/cases/materials) to (him/her) no later than (date), and I will spend (amount of time) training (him/her) in (roles/responsibilities).
Thank you for everything you've done for me in my (amount of time) here. I will greatly miss you and the rest of the staff.