IcoFX is an image editor primarily designed for icon creation, extraction and editing. It supports png, gif and bmp file formats. One of the best features for pixel pushing is the hue shifting, trans BG options and the ability to zoom in up to 10,000% (for comparison, Photoshop can only zoom to a maximum of 3200%). Unfortunately though, it only has a maximum canvas size of 256 x 256.
The program is compatible with Windows XP, Windows Vista, Windows 7; to download and/or read further about the program click here.
Originally sent in as a link by avo, but it's worth sharing on the front page too :)