Ok, top ten... let's see...
1. Spoon - simple and easy to make and the most essential eating utensil you can carry.
2. Tongs - There are a variety of methods of making them but the split (green) stick works best taking into account the amount of work put into making it.
3. Pot hanger - The method that uses a 'V' and an inverted 'V' dug into the ground to hold an angled stick above the fire works best if the ground is suitable. Otherwise you can use tripods or two 'legs' about 3 foot tall with a 'v' at the top with a stick resting between them and the pot hanger hanging from it.
4. Tent pegs - very useful.
5. Cocktail sicks/skewers - useful for eating.
6. Cordage - time consuming to make but an endless amount of applications.
7. Tent poles - for your tarp or shelter. Saves a lot of room in your pack.
8. Baton - if you have a good stout knife then this can save carrying an axe.
9. Bed - dry ferns, dry moss, spruce boughs, pretty much anything dry and soft. This saves a lot of room in your pack but materials need to be in abundance.
10. And last but definately not least.... Fire! - sounds obvious but you don't need to carry cumbersome and heavy cookers, you lose that risk of dangerous chemicals in your pack and you gain the good feeling that a camp fire gives that you just don't get from cookers/stoves.
This little lot could save anything between 5kg and 20kg in weight depending on the kit you may take in it's place, plus about 20-30litres of space in your pack. That's both side pouches of the average bergan free'd up