An issue of Shonen Jump that my sister bought me for a birthday present. It's one of the last things she ever bought me, so it means a lot to me. It's got several different manga in it, including some color Bleach manga. To this day, it's probably my most cherished gift I ever got from my big sister before she passed away. That's what my first manga was, a Shonen Jump issue. Not as concise as the rest of the answers but I hope it still counts.