Knife! Yes, I have my "CIA" knife in my Fanny pack. I use it all the time. Not on daring secret missions but mostly to open up those bubble tight plastic containers. Used it today as a matter of fact.
I usually carry my Victorinox "Officier Suisse", which has wood saw, hack saw, ruler, scaler, hook remover, scissors, pliers, magnifying glass, phillips head screw driver, large flat head screw driver, small flat head screw driver, tiny flat head screw driver, micro flat head screw driver, can opener, bottle opener, cork screw, ball point pen, tweezers, tooth pick, pin, file, grapple hook, leather punch, chisel, some silly stuff that I'm not sure what to call it, and yes, even a big knife and a little knife.
Come to think of it, I'd better get a fanny pack for all this crap! :)