Well, I live in NW Oregon... so rain is the biggest obstacle.
My five usually are:
Magnesium Flint Striker (Fire Starting)
Metal Coffee Can w/lid (Cooking, Boiling, Storing, Water Carrying, Trapping, Etc)
Belt Knife (General Use, Wood Splitting, Protection, Tool making, etc)
Emergency Blanket (Rain Proof Shelter, Rain Catch, Signal, etc)
Axe (Firewood, Shelter Building, Protection, etc)
And my sixth is my puppy, Raiden (Comfort, and Entertainment)