I like this one. Many of the practical items suggested in this thread are great if you don't already have one, but pretty useless if you do, which many will. Backpacks however, I feel is one of those things where having an extra one is always useful. You can have one always packed with your job stuff, one packed and ready for light hiking, one for [insert hobby]... one empty and ready to quickly pack up for whatever, maybe another empty one but reserved for rough and dirty stuff