MyPaint - MyPaint is a fast, distraction-free, and easy painting tool for digital artists.
PixBuilder - Free Photo Editing Software for PC
Microsoft Paint - Paint (formerly Paintbrush) is a simple, ultra-basic graphics painting program that is included...
PhotoDemon - Lightweight portable BSD licensed photo editor for Windows focused on performance and usability.
GIMP - GIMP is a multiplatform photo manipulation tool.
Fotografix - In addition to being totally portable, Fotografix has a ridiculously small footprint.