Never leave home without my Buck knife securly tuked in my right back pocket. Most of my friends kinda laugh about it but there have been more than a few occasions that it has come in handy and they are happy I had it.
I also carry a letherman in my school bag,( I am in college) and it also has come in handy.
I did for a while also have a Vicnox card by swiss army that goes in your wallet, but forgot about it when going thru airport security, I was bummed but it went bye bye. Now I have a little multi tool that goes on my key chain and looks like a key. I still miss my Vicnoix card.