Here are some of tested and suggested mods for Giants. If you have more that you'd like to share here is the exact place.
Note. It is better to test each mod with gog installer first before you add new one to this topic.
1. Graphical Revision Mod
Improves various visual aspects of Giants. Includes high resolution textures, enhanced shadows, new weapon trails, new weapon explosions, and weather effects.
http://www.giantswd.org/?file=31&search_name=Graphical+Revision+Mod+v1.01&search_author=&search_type=&search_db=&sort=Name&Submit=Search
2. Map Pack 1
Several maps for Giants.
http://www.giantswd.org/?file=31&search_name=map+pack+1&search_author=&search_type=&search_db=&sort=Name&Submit=Search
3. GeForce 3 Converter
Adds bumpmapping, weather effects, sky reflections, and new textures for newer video cards.
http://www.giantswd.org/index.php?file=31&search_name=geforce+3&search_author=&search_type=&search_db=&sort=Name&Submit=Search
4. Giants Enhanced
Adds multiple Kabuto support, up to four mecc teams, and team balancing options.
http://www.giantswd.org/download.php?offsite=0&id=378&d=patches/patch-giants_enhanced.zip
5. Giants Mod Manager
Allows you to play custom maps.
http://www.giantswd.org/index.php?file=31&search_name=mod+manager&search_author=&search_type=&search_db=&sort=Name&Submit=Search
6. GiantsHook v1.00
Adds a great deal of additional functionality to Giants in addition to fixing many bugs and glitches. For a current listing of GiantsHook's features.
http://www.giantswd.org/?file=31&search_name=hook+&search_author=neo&search_type=&search_db=&sort=Name&Submit=Search
7. Erotic Reaper
This erotic Reaper makes every guy get fantasies...
http://www.giantswd.org/?file=31&search_name=erotic&search_author=&search_type=&search_db=&sort=Name&Submit=Search
8. Giants Skin Manager
Tool to apply many skins fast and easy.
[url=]http://www.giantswd.org/download.php?offsite=0&id=608&d=tools/Giants%20Skin%20Manager.zip[/url]
For more files visit eg. http://www.giantswd.org/