Aseprite
Animated sprite editor & pixel art tool
Aseprite is a program to create animated sprites. Sprites are composed of layers & frames as separated concepts. Support for color profiles and different color modes: RGBA, Indexed (palettes up to 256 colors), Grayscale. Animation facilities, with real-time preview and onion skinning. Copy & paste. Drag & drop. Resize palette. Palette entries with alpha value.