Paint is small and fast; that's about it. Use Paint.NET, at the very least, if you absolutely refuse to use anything else.

I agree with Allstone above. I use paint for quick and small pixeling and Paint.NET for anything else, but I'm not an artist.

I know this is a necro but this actually matches to what is being said above me. I use paint.net and when I save the image of a rifle. In game it looks all wierd and inverted colors, random lines through it and then my guy's chest doesn't show up. What am I doing wrong? I save it as a .bmp too. Oh and I use paint.net.