Aseprite - Aseprite is an art program dedicated to the creation of pixel art.
IconLover - Icon editor for Windows.
Pixelorama - Free and open source sprite editor and animator, ideal for pixel art.
VistaCreate - The VistaCreate is a free and global digital platform which is known for sharing, searching, finding, and creating great art.
Piskel - Piskel is a website where designers online create sprites or pixel art.
Lospec Pixel Editor - Free online pixel art program. It's easy to use, intuitive and unobtrusive.