Dear (insert manager name here)

After an appropriate period of deliberation, I have come to the decision to tender my resignation from (Company Name), effective (date).

Please know that I still maintain a high level of respect for you as a manager and colleague, and I thank you sincerely for the support and assistance you have offered me in each of those roles. I have been proud to work for (Company Name) over the past twelve years; it has been a journey that has provided me an unparalleled foundation to move forward to new and exciting opportunities.

As such, I have decided to become a professional pirate. It has always been a dream of mine to live the life of a swashbuckling corsair, beholden to none and master of all I survey. Once my crew of unabashed rogues is assembled, we shall take to the capacious expanse of the high seas to pursue fortune, fame, and hair-raising adventure.

Our path may not be filled with the porcine comforts and technological marvels that (Company Name) provides, but we shall nonetheless move forward to carve a name for ourselves in the annals of bold insurgency and death-defying derring-do. Once I have a keen blade at my hip and the Jolly Roger is flapping high above me, I believe I will find my true calling.

Please note that I am currently accepting applications for First Officer, if you are at all interested in applying. I will provide a full medical and dental plan, which will offer immediate coverage of all maladies other than scurvy and the occasional bout of rickets.

Sincerely

(Your Name)

[note - i did not write this, it was found on a forum where even the OP did not know where it came from as they had found it several years ago but i felt it was too epic not to share so enjoy :D]