Decent free G-code editor?

Hi All,

Is there a decent visual G-code editor out there?
I dont want something to create my toolpaths (as I have these already)
but something I can use to safely pull out unnecessary G0 X0 Y0's that
seem to arise when I concatenate multiple toolpaths together. Also,
changing things like "G01 Z-5 F<SNAILSPACE>" so they rapid down through
what's already been cut first and then plunge what hasn't, rather than
starting plunging slowly from my safeZ.

Free, or very cheap would be good, too...

Cheers!
Abby