X3 Editor latest version 0.0.15 - released 9.3.2007
Download from www.doubleshadow.wz.cz.
Don't forget to download the DevIL plugin (available at X3E download page) so you will be able to see Missile and Laser icons.
There is X3 Editor page on X-Wiki which can point you to other useful info and tutorials.
If your antivirus gives you a warning about X3E or X3MM patch, read Virus issues with doubleshadow's tools on X-Wiki for possible reasons.
Changes:
* fixed bug in TLaser which forbid you from change the Projectile (bullet) type
Description
X3E is successor to X2E

You can:
Edit and add new records into most T files.
Edit TShips files (adding turrets, lasers, ...)
Galaxy Editor and Text Resource Editor:
Both editors are fully functional as viewers but their ability to save files may be limited as they were designed for X2.
If you are new to X3 modding, you should also read how to make a mod using X3 ModManager.