1-2 extra sets of BDU's
6 or more pairs socks
3 pairs underwear
3 T-shirts
Jacket (M-65 or similar)
Light gloves
hat/balaclava/watch cap
Large first-aid kit
Personal Hygeine kit (don't forget T.P.!)
Extra ammo for assault rifle/MBR and for sidearm
Weapons cleaning kit
Camelback and/or more canteens
3-5 FULL MRE's
MRE snacks/energy bars/etc.
Water purifier
Emergency space blanket
.22 pistol w/ minimum of 100 rounds (for foraging and taking small game)
Other Possibilities(if room in pack):
Rope
Sleeping bag
MRE heaters
deck of cards