In GIMP, you can (in various modes) draw a constrained straight line which will "snap" the line you're drawing to the nearest 15 degree angle, making it easy to draw lines in a precise direction. For example, in paintbrush mode, you do this by clicking one point, releasing, holding shift+ctrl, then moving the cursor to the next point of the line and clicking.
Is there any way to do this in paths mode? I can't seem to use this method to get an exactly horizontal path segment, for example.
Possible with the free Selection tool. Then go to Select -> to path. You'll see you path in the Paths toolbox.