This page is incomplete! You can contribute information using GitHub issues or pull requests.
H3 ODST Guerilla (guerilla.exe) is part of the Halo 3 ODST Editing Kit, is a visual tag editor. Although it can visualize bitmaps and is primarily focused on editing and viewing the structured fields which comprise tags. It does not offer ingame previews or interactive placement of objects, which is Sapien's role.
It's pretty much identical to Halo 3 Guerilla so please refer to that page for further info on hotkeys and features.