Legend of Mana, it's an entry in the Mana series for the PS1 that was nothing like the other Mana games of the time (Secret of Mana, Seiken Densetsu 3, etc). It features 2D sidescrolling combat and long but sporadic and unrelated story arcs. The series itself started off as an offshoot of the Final Fantasy series, interestingly enough.
Anyway, Legend of Mana is a huge piece of nostalgia for me. I played it obsessively throughout my childhood and recently fell in love with it again. Some of the best music and art style to come from the PS1 era, in my opinion. It was met with mixed reactions for it's departure from Secret of Mana/Seiken Densetsu 3's combat/story. But to me it's one of the best games I've ever played.
You can craft your own weapons, create magical instruments to use in battle, raise monsters to fight alongside you, organize the overworld however you like, meet a diverse amount of companions, and so much more. It has breadth and depth for a PS1 game. At the very least, if you're interested, check out some of the art style/music/combat on youtube. It's a wonderful gem of a game, and I hate using the word gem unless it really applies.