I am mostly right-handed. Do all my casting with the right and reel with the left. Have my fly reels set up for left hand but will cast fairly well with the left when the wind is from the right. Keeps the line out of my hair.

Turns out that I tie flies left-handed. That was just the way I set up my vise. Made it interesting when my instructor, who was right handed, tried to show me a whip finish.