1

Inkscape

This is a free and open-source vector drawing software with a range of features such as Bezier curves, shape tools, and text support.

2

Krita

2D drawing software, with a range of features such as brush stabilizers, layer masks, and animation support.

3

GIMP

it's an image editing software that offers tools for editing digital art. GIMP is a free alternative to Photoshop.

4

Blender

Blender is a 3D modeling software that can also be used for 2D animation. It offers features such as rigging, rendering, and animation tools.

5

MyPaint

It's a painting software that is ideal for creating digital artwork. It offers features such as infinite canvas, brush customization, and pressure sensitivity.

6

Piskel

This is a free and open-source sprite editor that is ideal for creating pixel art. It offers features such as layers, frames, and export options for various platforms.

7

GrafX2

This is a free and open-source bitmap painting software that is ideal for creating pixel art. It offers features such as layers, palettes, and animation support.

8

Vectr

This is a free vector graphics software that can be used online through a browser. It offers features such as real-time collaboration, shape tools, and text support.

9

OpenToonz

It's a 2D animation software that offers a range of features such as vector tools, bones animation, and compositing.

10

Synfig Studio

It's a 2D animation software that offers features such as bones animation and is more suitable for complex animations.

For free 2D sprites, check out the list of websites that offer free 2D sprites for your game.