Trying to pick that one knife to carry is tough, which is why (knife type dudes) have a few they rotate in and out of service. Kinda like girls with purses I guess. A good choice for those on a budget who just want one great knife should take a look at the Gerber Epic Knife.
The Gerber Epic Knife has a chrome-molybdenum stainless steel blade with a serrated edge, a blunt tip, a nylon handle, a locking sheath, and a bottle opener. The best part, other than the bottle opener, is the price, only $30 here.