I feel like I have a new favorite every few years..
This is one part of my gear that seems to change more frequently than anything: the bags I use for daily use, travel and specific needs like photography. As much as I'd love to find one do-it-all bag, I really think they are all task-oriented and I won't be able to get away from having a few depending on what I'm up to.
A basic, no-frills backpack I found on sale for $29 in store. It's my go-to for going around the city and running errands. Not protective enough for a laptop without a sleeve though.
34L, Special Forces-grade materials
Patagonia Black Hole duffel
Lightweight, weather-resistant, folds flat. I have this in both 45L and 60L sizes. Great as an extra bag for bulky things when traveling.
Away Expandable Carry-on, Soft-shell
I have the carry-on size of a now-discontinued soft-shell version of the Away Expandable Carry-on suitcase.
Peak Design Everyday
This is the workhorse bag. It's the bag I pick when I go on any kind of trip with my camera. It's rugged and the bag has a bit of structure to it (somewhere between soft and hardshell) so I trust it to keep whatever cameras I have inside safe, especially when tucking into a tight compartment underneath the seat in front of me on a flight.
I initially disliked the adjustable internal compartment system because I felt it left my lenses too loose and free to roll around compared to my former Incase DSLR Pro Pack but I have come around to loving it. The handy magnetic flap and waterproof construction makes it great for weathering the elements. I also like that it has some straps that you can extend to attach other gear to the bag, which I commonly use when lugging around my tripod.
I had the original charcoal version but unfortunately after a year or two I had some premature wear on one part of the bag so I purchased a new black version at a discount with the warranty.
I never check my bags when I fly anymore, and try to fly with only a backpack when possible. I've always wanted to pack lighter and fit everything into one backpack. After a bit of research, it seemed like this Goruck was the one for the job. Extremely durable, tons of compartments and add-ons that can be strapped into the MOLLE webbing system. I also have the padded GR2 field pocket add-on. I've taken this on countless short work trips and I lived out of it for a month while traveling through New Zealand. The GR2 is fairly no-frills, heavy and rugged.
Patagonia Black Hole duffels
I originally purchased a 45L duffel as I needed something lightweight and soft for my trip to Africa, where it would have to be squished the cargo bay of a small Cessna (we had a strict 33lb limit for all bags, including camera gear so I thought the GR2 was a bit too heavy and rugged). The Black Hole duffels are affordable and versatile enough to be worn like a backpack and crumpled down to a tiny size when not in use (they fold neatly inside themselves).
I found myself using the duffel on other trips afterwards and ended up adding a larger 60L model as well. I still use them as carry-ons.