MtPaint
From OHRRPGCE-Wiki
mtPaint is an Open Source graphics editor specificly designed for pixel art. It is developed on GNU/Linux, but there is also a Windows version.
NeoTAs opinion: It's very easy to use and fairly powerful. For learning to pixel, I recommend this over GIMP. GIMP has more power, but it's harder to learn. If you're used to pixeling, use GIMP or Pro Motion instead.
