Photoshop CS6: Line tool prints arrow instead of line

If you're looking for the arrowhead options, it's located on the gear (default position):

If that doesn't work, try to reset the line tool:

This thing has been giving me a headache too! I finally found the answer myself.

Do you see the arrow drop-down menu next to the Custom Shape tool? There is a check box for Start and End. Uncheck them both, and it will draw a line instead of an arrow!