Aseprite - Aseprite is an art program dedicated to the creation of pixel art.
Texture Studio - Texture Studio is all you need to produce professional quality textures for use in games and tiled...
Pixen - Pixen is a professional pixel art editor designed for working with low-resolution raster art, such as those 8-bit sprites found in old-school video games.
Resprite - High-performance pixel art editor with advanced layer and timeline systems
TextureLab - Free, Cross-Platform, GPU-Accelerated Procedural Texture Generator.
Pixelorama - Free and open source sprite editor and animator, ideal for pixel art.