Some tools that are simply too valuable to live without (for me anyways):
-Any batch rename script
-My texel density script for auto-scaling every UV-shell so that the TD becomes the same for them all.
-Xform UV for stacking UV-shells and best of all: orienting UV shells. I can’t believe I spent so much time without a proper tool for orienting UV-shells.
-File Texture manager from Crow Yeh.
-Roadkill UV: It’s an old, abandoned tool but imo it’s really, really awesome. Extremely easy to use, good and fast unwrapper AND it comes with a superb stretch shader for finding pinching and stretching on your models.