Here is a windows command prompt application that I wrote to help you find important locations in your Dead Island GS. I call it DumpDI.

http://www.mediafire.com/?81ox388i6zq466x

When you enter DumpDI at a command prompt you should see this:

C:\Download\Game\DeadIsland\GS>dumpdi
This routine will take an unencrypted Dead Island Game Save file
and display everything that I have found it to contain.
Useage for DumpDI Version 1.00:

>DumpDI filename

C:\Download\Game\DeadIsland\GS>

when you run it the output could scroll off your screen so redirect the output to a file instead. I use x.txt. Here is what it looks like on my save_1~ GS:

C:\Download\Game\DeadIsland\GS>dumpdi save_1~ > x.txt

C:\Download\Game\DeadIsland\GS>

My Hex Editor of choice is HxD. It is available for free from:
http://mh-nexus.de/en/downloads.php?product=HxD

Before we look at the contents of the output of DumpDI stored in X.txt let me tell you of what to me seems obvious. However I understand it probably requires a little explanation to someone else.
There will be lines in it that look like this:

1234: <<<some text>>>

On the left you will see four hex values followed by a colon and on the right is what starts at that location. Often I have already stated it in a converted form. However if you examine things using HxD then starting at that location you will see the actual raw hex prior to any conversion algorithms.

The locations are not fixed. That is while they work on your current GS that you ran a DumpDI on. The moment you change the size of your GS through editing or playing the locations will most likely shift elsewhere.

For all items I use the following:

1234: 1 @000 WHT Some_Item Some_Mod, 1234FEDC, -1.000

Again on left we have 4 bytes followed by a colon. Yes this is still the location of first byte in this case for the item.

following that we have a 1. This can be any number and in most cases it is the quantity or ammo.

Then we have the upgrade level which will always be one of the following:
@000 = 0 = No Upgrade applied (fair)
@@00 = 1 = Upgraded Once (good)
@@@0 = 2 = Upgraded a second time (better)
@@@@ = 3 = Upgraded a third and final time (best)
???? = N = some other number, usually an indication of an error

Then we have WHT which is the items rarity however it is mostly applicable only to weapons. The rarity is as follows:

WHT = white = poor and very common
GRN = green = good and hard to find
BLU = blue = great and difficult to find
VIO = violet = excellent and extremely difficult to find
GOLD = orange = Legendary and most rare!

This is in turn followed by the Item name and then the Mod name followed by a comma.

The 8 hex bytes of Required Level are presented. It is important to note that the last nibble I.E. very rightmost 4 bits of rightmost byte in Required Level is Rarity. That is also followed by a comma.

The final value on the line is the Condition. For items this value is normally -1.000. If you examine the hex you will find a location that has BF 80 00 00 in it. That is the unconverted byte representation of a floating point number that is -1.000.

And now without any further interruption here are the contents of x.txt:

Filename In <save_1~>
Starting...
reading in file...

002C: <<<3 Strings>>>
ACT1A
HubChapter_1
auto_SP_RH_Sinamoi_Hut

0061: <<<Play As>>>
Type;Purna

006F: <<<Chapter 2>>>
0071: <<<Level 2>>>
0079: <<<Active Quest>>>
ACT1A_Sinamoi_Busy

008D: <<<Complete 8%>>>
0099: <<< 32 min 35 sec>>>

00D4: <<< Data Len 1 = 3367>>>
00D8: <<< Data Len 2 = 3363>>>

00E4: <<<10 UnHeld Weapon Items>>>
Loc Qty Upgrade Item Mod, Req Level, Condition
00E8: 1 @OOO WHT Melee_PaddleBattered None, 1145F400, 14.000
0114: 1 @OOO WHT Melee_BrassKnucklesLightGen None, 3385CC08, 35.012
0147: 1 @OOO WHT Melee_CrowbarGen None, 30B74408, 32.421
016F: 1 @@@O WHT Melee_KnifeDivingGen None, 3C5D3408, 18.124
019B: 1 @OOO WHT Melee_KnifeDivingGen None, 0AEF7808, 19.187
01C7: 2 @OOO WHT Powerup_Alcohol None, 00000000, -1.000
01EE: 1 @@@O WHT Melee_KnifeDivingGen None, 3C5D3408, 13.124
021A: 1 @OOO WHT Melee_BrassKnucklesGen None, 1D022808, 31.432
0248: 1 @@@@ WHT Melee_KnifeDivingGen None, 70D5D008, 25.552
0274: 1 @OOO WHT Melee_CleaverHomemadeGen None, 71205410, 13.544

02A8: <<<0 Jin's Inventory Items>>>
Loc Qty Upgrade Item Mod, Req Level, Condition

02B0: <<<20 Misc Items>>>
Loc Qty Upgrade Item Mod, Req Level, Condition
02B4: 3 @OOO WHT CraftPart_Nails None, 00000000, -1.000
02DB: 4 @OOO WHT CraftPart_Water None, 00000000, -1.000
0302: 3 @OOO WHT CraftPart_FlexibleHose None, 00000000, -1.000
0330: 3 @OOO WHT CraftPart_Magnet None, 00000000, -1.000
0358: 3 @OOO WHT CraftPart_Wire None, 00000000, -1.000
037E: 4 @OOO WHT CraftPart_Tape None, 00000000, -1.000
03A4: 2 @OOO WHT CraftPart_ElectronicScrap None, 00000000, -1.000
03D5: 2 @OOO WHT CraftPart_Belt None, 00000000, -1.000
03FB: 1 @OOO WHT CraftPart_Clamp None, 00000000, -1.000
0422: 1 @OOO WHT CraftPart_Deodorant None, 00000000, -1.000
044D: 1 @OOO WHT CraftPart_GasForLighter None, 00000000, -1.000
047C: 1 @OOO WHT CraftPart_Gear None, 00000000, -1.000
04A2: 1 @OOO WHT CraftPart_EngineParts None, 00000000, -1.000
04CF: 1 @OOO WHT CraftPart_BarbedWire None, 00000000, -1.000
04FB: 1 @OOO WHT CraftPart_Detergent None, 00000000, -1.000
0526: 1 @OOO WHT CraftPart_LemonJuice None, 00000000, -1.000
0552: 2 @OOO WHT CraftPart_Battery None, 00000000, -1.000
057B: 1 @OOO WHT CraftPart_Bolts None, 00000000, -1.000
05A2: 1 @OOO WHT CraftPart_Lighter None, 00000000, -1.000
05CB: 1 @OOO WHT CraftPart_SteelRod None, 00000000, -1.000
00000001 1

05F9: <<<3 Hold Slots>>>
Loc Qty Upgrade Item Mod, Req Level, Condition
05FE: 1 @@@@ WHT Melee_KnifeDivingGen None, 70D5D008, 18.552
062B: 1 @OOO WHT Melee_Fists None, 4BCC6800, -1.000
064F: 1 @OOO WHT Melee_HeavyPipe None, 2DCC5400, 20.000

0785: <<<Level 2 2nd Loc>>>
0786: <<<XP 3149>>>
1 078F 00000000 0
2 0793 00000000 0
0792: <<<Level 2 3rd Loc>>>
00 00
079C: <<<1 Nodes in Skill Tree(s)>>>
Loc Skill N/3 ZERO
07A0: 0029 1 0
07AC: <<<1 More Nodes in Skill Tree(s)>>>
Loc Skill N/3
07B0: 003A 1
0834: <<<4 collectables found>>>
Loc Hex Decimal
0838: 0000007B 123
083C: 000000A2 162
0840: 00000101 257
0844: 0000007C 124

<<<0 Quest Givers>>>
0858: <<<Checkpoint>>>
HubChapter_2_3_4_9

0874: <<<Cash $452>>>

0878: <<<Beyond This Point Lies The Unkown>>
j= 2169
save_1~ has 4,173 bytes in it