I don't carry one in my bag, but I usually carry a
Victorinox Spartan pocket knife in the back pocket of my jeans. It's a simple two-layer model, but manages to pack in large and small blades, can opener, 3mm and 6mm flat screwdrivers, bottle opener (important
), corkscrew (
vitally important
), wire stripper, reamer, punch, toothpick, tweezers and key-ring. I also have the mini screwdriver accessory (for spectacles etc.) that threads into the corkscrew for storage.
I've had my current Spartan for many years (20+, I'd guess), and the scales are looking very dulled and battered now... but aside from that, it's as good as the day I bought it. For me, it's the perfect tool. I also have a
Victorinox pocket sharpener which includes a grinding stone and ceramic "V" notch, and does a really good job of keeping the knife blades near-razor-sharp. It takes a good while for Victorinox pocket knives to lose their edge unless you really abuse them, but like any other knife they benefit from occasional sharpening and/or honing.