-Dark Injection created by Davo, now developed by rob55rod - This is imo the nr 1 mod to absolutely have for your spore game. It adds tons of content from darkspore such as creature parts and creature armor, edits spores UI to look more like darkspore, gives you tool parts like invisible limbs and individual ability parts, disables the complexity meter and so much more! And it even comes with force save bundled. It has a handy installer too, so you can easily choose what you want to add in your game and what you want to leave out.
-Infinite scaling mod by Zarklord - This i think is absolutely essential in complete creative freedom. This mod gives you the ability to enlarge or shrink any part in any editor and allows you to really get into detail without being held back. Note that things that are too big could cause glitches.
-Enchanted color picker - by Emd4600 - Another color mod, but this one gives you thousands more colors for your creatures skinpaints then what spore currently has to offer, and gives you more spesific control over what you need.
-Project Bacterioid by IHaveNoIdea. A mod that unlocks the cell editors true potential. Makes the cell editor 3D, adds creatureparts and limbs, adds rotation and morph handles, and more. A good mod for making much more complex cells to have fun with.
-CamBen color pack - by CamBen. Adds plenty of parts in different colors and shades to your editor, making you able to have much more control over what colors your creature is. This gives you more creative freedom and makes you able to finally make that big rainbow cat you always wanted to make.
-Adventureprops - by CamBen. - One of my favorites, this one adds plenty of props to the adventure editor. You can create so much more stuff with what you get from here, more gates, citywalls, space props, sattelites, more effects and so on. Really recommend this one!
-Himeric Engine - by Clicker95 a really cool parts mod that add high quality and realistic alien parts, allowing for some pretty unique creations. The textures are a bit weird but they work just fine. THE LINK IS NOT DEAD!! just scroll further in the thread, a reupload has been posted.
-INTEGRATED INTEGUMENT akaThe Fur Mod - by Disgustedorite - This mod was once thought to be impossible...its the FUR MOD!! This handy mod gives you 4 different fur creature parts so you can finally add some real fuzzy charm to your creations. Comes in 4 types of Thickness and different levels of color, so you can really get more creative opportunities.
-Strange and Beautiful - by peridot - A mod that adds tons of high quality parts, with differnt animations such as a tounge sticking out, when a mouth opens, or bunny-like ears that bends along with your creature. Although it suffers from a few visual bugs, i really recommend this one.
-Drone parts - by Deoxys_0 - Do you want to make your robot creature even more robotic, but would rather build it with simpler shapes? Or have complete control over building better armor and robots? Then this is the mod for you! it adds plenty of pages full of robotic parts from machine gun nozzles to simple cubes, all in different coat layer coloring. A high quality mod for making high quality robots...or drones!
-Citywalls - by Frogottenspore - A mod that allows you to change the walls to your space and civ cities. I personally love this one because you can use it to get grox walls or a "ruined city" look. there is an old version on Forgottenspore, but its old and outdated and Darhagonable is working on an improved verison, which i am contributing to also :3
-InfiniteSOL - by ??? - a mod i think its almost neccecary..because once you get the staff of life, you basically get a reward for winning the game....but..you can only use it 42 times, which i think is BULLSHIT! so..yeah, use this if you want your PROPER reward. It removes the limit and makes the staff infinite uses.
-Grox archetype - by D3vilSheep - so many has dreamed about playing as the grox, and with this one you KINDA can. It replaces the knight archetype in space stage with a "grox one" aka replaces your aliens voice, background and lighting effect with the grox ones. Mix this with the citywall mod to give yourself the grox citywalls and your almost a complete grox. This works in CIV stage as well.
-Empire voice replacement - by Kisutora - Are you tired of hearing your alien 56-mouthed lava sheep empire having the voice of a normal human from the sims? Well no longer shall you suffer, for this mod replaces the voice of your empire with any other archetype voice of your choosing. This DOES include the grox voice as well, but if you want the complete grox package with bg and lighting included, i suggest you take a look at the grox arcetype one above.
Theres also two tweaks that you can do to your game that i feel will also make your experiences the game itself better: The 60 fps fix and The Shiny graphix fix. The 60 patch just removes the 30 fps cap and makes it 60, while the shiny fix makes your creatures skinpaints appear in higher resolution, aka makes your metallic or shiny creatures actually shiny or metallic. i wouldnt reccomend going above 2048 unless you want tons of crashes.
These are it for now, but i might add more. if you have a must-have mod you feel is needed on this list, or there is something on this list that is wrong, let me know