A Swiss Army Traveler has gone everywhere I have for 40 years. It's supplemented by a fully serrated Spyderco Delica in the other pocket for jobs a plain edge can't handle. I have many others, but they stay home most days.
Bought 3 of these Spyderco Tim Wegner folders on Ebay after they were discontinued for around $60-65 each(retail was around $165). I've been carrying one everyday for about 15-16 years. Lost one somewhere and one needs to be sent back to Spyderco to be refurbished. Absolutely love them!
I carry a Lightning Double Action Out The Front Automatic Knife. Fast and easy to open and close, can be done without drawing attention to you even opening. Only need to use your thumb to open and close.
Its been clipped to my pocket for 5 years now.
The handle started getting pretty deteriorated from my working with some nasty solvents that I should have kept away from it, so I sent it back to Benchmade last year expecting to have to pay for replacement, but nope. In fact, I think they replaced everything but the blade, but they sharpened to to a razor edge and sent it back to me and didn't charge me one cent!
I carry two every day. One is a CRKT M21-10KSF. I like the fact that the skeletonized handle makes it very light but sturdy. The flipper acts like a small tang, too. The price was also right -- so I don't worry about losing an expensive Benchmade!
The other is a small Boker in my pocket. With the paracord, it's easy to grab in my pocket even with other stuff in there.