brush tools;

bucket fill;

The bucket fill tool fills an area (either of selection or similar colours) with a colour or pattern.

blend/gradient;

The blend/gradient tool fills an area with a gradient (of both the foreground and background colour or an existing gradient).

pencil;

The pencil tool paints hard-edged lines - not anti-aliased.

paintbrush;

The brush tool paints smooth or fuzzy-edged lines - anti-aliased or feathered.

eraser;

The eraser tool erases pixels from a layer

airbrush;

The airbrush tool is a paint tool with variable pressure (pressure can vary).

ink;

The ink tool paints anti-aliased lines (with a simulation of a nib).

clone;

The clone tool copies pixel from one part of an image to another.

heal;

The heal tool heals irregularities in an image.

perspective clone;

The perspective clone tool allows you to clone a part of an image according to the perspective you want.

blur/sharpen;

The blur or sharpen tool can blur or sharpen an image, alternatively.

smudge;

The smudge tool spreads pixels in a specific direction.

dodge/burn;

The dodge or burn tool lightens or darkens an image's shadows, mid tones or highlights.