Take a look at the Victorinox Swiss Army Knives. There are quite a few slim, lightweight, ones in the range that don't have all the tools that makes the larger knives heavy and bulky for EDC. Heinnie Haynes and Amazon stock them, cheap, and decent quality. I've got a couple of SAKs, and often carry the 'Waiter' knife in the UK. More than adequate for opening boxes etc.