My wife made fun of me when I bought this and added to my keychain but she quickly admitted that it's proven useful already on several occasions.  Most often it's great for opening the impossible to open plastic clamshell packaging that almost everything is packed in nowadays.  It's also opened the fancy beverages that come in old fashioned glass bottles without screw tops.  Removing tags.  Opening mail without having an envelope that looks like it's been mauled.  Filling out the order menu at Din Tai Fung when they don't leave a pen, signing a bill when they don't leave enough pens for the table...  Best of all it's small and I don't feel like it's made the keychain more unwieldy.