The one that started it all... Before Fromsoftware known for its dark fantasy game. Like Dark Souls, Elden Ring, Demon's Souls & Bloodborne, Fromsoftware excel & known for making mecha games and also one of foundation of Fromsoftware, is Armored Core.
Armored Core released in 1997 is by far the best mecha games for its customization at that time. You can customize your Armored Core/AC's (Main mecha/Your "character" on the series) head, body/core, arms. legs, weapons, equipment & also the internal parts like FCS/Targeting System, Generator & booster. You can also color individual body parts and also make your personal emblem. And that emblem also gonna appears on your AC's arms & some of weapons. Its definitely pretty awesome technology on PS1 that time.
The storyline & missions are also great for its time. Jump into dystopian mechanized corporation warfare theme with variety of mission. Like destroy enemies, defending, sabotage, recover lost technology, assasination, explore unknown area, & even some betrayal, twists & turns.
That's why Armored Core should be preserved, currently it still locked on Playstation hardware. But more people should play & experience Armored Core this legendary series from Fromsoftware.