Mine is Berserk, it's really awesome and immersive. Also, it motivates me to work-out and live my life to the fullest. If you write your favorite manga, please add an explanation why it is your favorite.
If you need suggestions try mine such as Hajime No Ippo , One Piece, Fairy Tale, Bleach and Naruto these manga's has a lot of learnings that you'll gain. Have fun.