MS Saga: A New Dawn - an RPG using the Gundam franchise in an original story. The customizing of load outs, optional equipment, and mixing of mech parts is one of the best in any RPG that I have every played. Tactics are essential (it's not the "equip best gun/missile/sword and you're good" type of game) and it's easy to spend over 99 hours just enjoying the game.

But it's also a VERY niche game.