Line Tool No Longer Allows for Pixels?

I never want to use the line tool to create a shape or a path. I constantly use it as a straight line tool for pixels only. Suddenly it seems that this is a greyed out unselectable option. 

Is there any way to use the line tool for pixel creation only? I do not want to go through paths or shape tools to eventually create pixels. I only want to use the line tool for creating pixels.