1. A guy who, whilst being straight, enjoys a finger in his rectum during sexual relations. Also known as a Finger Pilot
2. A person who enjoys putting his/her finger in men's anuses and playing with the prostate gland.
"Yo, bro, you gotta try it.. get your missus to stick her finger in your ass right before you blow, it's awesome."
"You're such a Walnut Tickler, cuz Cliff"