Alright I put a lot of work into this new skill tree. (Sharp Weapon Based)
I hope my instructions are clear enough.
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=-=-=-=-DOWNLOAD-=-=-=-=
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=-=-=-=-INSTRUCTIONS-=-=-=-=
How to apply the Ninja Skill Tree:
1. Go to your Dead Island installation folder.
Example: C:\Program Files (x86)\Dead Island\
2. Open folder "DI"
3. Open folder "Out"
4. If you don't have a folder called "data" in there, just create it and open that folder
5. If you don't have a folder called "Skills" just create it and open it.
By this point, your directory should be this:
"Dead Island\DI\Out\data\Skills"
6. Go into the download and open the folder for the character you want to play as.
(Note: All characters are equal in this mod, so just choose who you like the most.)
7. Copy both files "NAME_levels.xml" and "NAME_skills.xml"
8. Paste these 2 files into the "Skills" folder you created in step 5.
9. Start Dead Island.
10. Start a New Game (Because all effects won't be applied if you continue a game).

=-=-=-=-FEATURES-=-=-=-=
- Health is maximized at 330 at level 20 and can be increased by 3 bars from a skill.
- You get 2 Skill Points per level, at level 50 you have a total of 99 Points to spend.
- Those 99 Skill Points let you upgrade every skill in the Skill Tree.
- Jumping doesn't use Stamina
- Running doesn't use Stamina
- Sharp Weapon based Skill Tree
- Fury was changed from Xian's BloodRage to each character using their own Fury because for example Logan would pull out the knife but he wouldn't be able to attack with it.
- Start with all weapon slots unlocked(7)
And many other small features that make it all worth it.

This Mod can make the game very fun to play through again.
Tomorrow's Project: Gun Skill Tree, and then a Blunt Melee Skill Tree if I have time.