Süsse (Super ültra sweet sprite editor) helps you to create low-resolution sprite sheets.

Süsse can do things like this with just a few clicks:

Basic controls:

• Left and Right arrows to change the frame
• Ctrl + D deletes the last frame
• Ctrl + Shift + D deletes the current frame
• Ctrl + G shows/hides the grid
• Alt + C changes the palette
• Click while pressing B will perform a normal fill
• Click while pressing Ctrl + B will perform an 8-directional fill
• Click while pressing Shift draws a line
• Mouse wheel to zoom in or out
• Ctrl + Z for undo
• Ctrl + Y for redo

Süsse is still a work in progress, thanks for you feedback