Game Boy Advance Editors:
Breath of Fire ROM Editor (GBA/SNES)
Download Breath of Fire ROM Editor ver 1.1a
Also available at RHDN with a full description: Breath of Fire ROM Editor
Breath of Fire 2 ROM Editor (GBA/SNES)
Download Breath of Fire 2 ROM Editor ver 1.3
Also available at RHDN with a full description: Breath of Fire 2 ROM Editor
Fire Emblem ROM Editor (GBA)
Download Fire Emblem ROM Editor ver 1.0
Metroid Fusion ROM Editor (GBA)
Download Metroid Fusion ROM Editor ver 1.0
Can read about the editor here: Metroid Fusion ROM Editor development