Another thin arrow GIMP Python plug-in called 'ArrowsCreator'.
It's characteristics are:
-produces many different types of straight arrows
-produces one type of 'path' arrow
-facilitates combination of multiple arrows
-interactive with GIMP
-developed on GIMP 2.6 (work on 2.8 except no repeat gradient in shaft and GIMP don't control brush size).
ATTENTION: don't change layer during execution of the plug-in. Also on my computer begin to get sluggish for certain type of arrow in image greater than 7 Mpx.
The basic arrow types (0-5) in version 0.1, a blue 'multi-segmented' arrow and the initial window are illustrated below
After an extraction of the zip archive in the '.../.gimp-2.x/plug-ins' directory it should appears in GIMP under the menu: "(Image)/Extensions/Plugins-Python/Tools/Arrows creator..." or your choice at first start of GIMP .
[Edit 2013/04/11] version 0.2 compatible with GIMP-2.8
[[Edit 2014/05/09] Corrected some bugs and continue last edit. This terminate what I want to do for version 0.2 . From now only bug correction.