I carry at least three or four knives every day. I carry a key chain Swiss Army Ramble, sometimes a multi-tool, a larger blade knife like a Bedlam, Emerson Karambit, or SOG Architect, but one I figured I'd share is one I almost always have in my pocket that performs multiple roles; it can be used for everyday utility tasks, as a Self-Defense push knife or even a kubaton. This knife is the Paul Chen Citizen Knife (built I think on an Appleton Design) which is a 3 position lock knife with an added 'One-Arm-Bandit' thumb stud for instant deployment. I often give knives as gifts and have probably given away over 20 of these to friends that don't train as much as I with martial arts and with development and maintaining knife fighting skills. One reason I give it to folks is that with minimal training people can learn to open it quickly and use it if needed to escape a situation, it has great weapon retention capability and... it is a very good knife for everyday tasks. Adding the 'One-Arm-Bandit' was not a great modification, but it certainly extended its capability. I keep it razor sharp and I mean... razor sharp.
This was an inexpensive knife. I have two, but in all the years (15+) I have never had one fail for me.