I used to do survey in the jungle for years, minimum two weeks in the forest.
My personal list:
1. Machete (local blacksmith custom golok)
2. insect repellent
3. Cheap tobacco (as leeches repellent, we could use detergent but it is chemical)
4. matches/zippo (i don't have any fire kit yet)
5. wet tissue
6. Military issued poncho (multi purpose, we can use it as tent)
7. knife (copy of herder style by local blacksmith): i am waiting for my Izula and RC 5, have no time to pick it at Indonesian custom.
8. dry bag (we are in tropical rainforest), I used to keep a pair of clothes clean just in case i should meet with government officer on my way back to my office after weeks in the forest.
9. candies (i don't smoke)
10. Victorinox or leatherman (i have both) and Kathmandu nailclipper (issued by Kowell-Korea).
11. water bottle
12. water purifier (but most of time i rarely used it, just directly drink it from the stream)
13. extra supplement: vitamin B or high vit C such as CDR.
14. Compass
15. torch
of course the important things: logistic, we always put salt and chili in our first list

The very-very important things: GPS, all weather notebook, map, extra batteries for GPS camera and binocular also rangefinder.
Total weight 27-30kg per person of 4 people.
My friends love to bring their MP3 player.