Folding: CRKT M16-14 "Big Dog." I've owned a whooooole bunch of lockbacks in my time, and the CRKT is my favorite by a very large margin. I bought it for $85, at first not sure if a knife with four-inch blade and nine-inch OAL was a wise choice for a daily carry. But it's very slim and has a stout pocket clip and packs very easily--even easier than my last daily carry, a Gerber LST with pocket clip. The M16 is truely a one-handed knife that's practical; you can open it very easily (a little too easily - explained below) and close without having to flip it around in your hand. The big blade makes cuts easy, and I guess it could be used as a backup to the 1911.
On the easy opening - I once moved to stick it in my waistband and bumped the opening stud. The point of the blade came out just enough to jab me in the thumb. A small cut, but you bet your ass now I'm very aware of what part of the knife I'm touching when I pocket it.
Fixed: I can't for the life of me remember the model of Gerber fixed blade I have and enjoy. It's not as big as the other fixed blades I own; I seem to like the larger folders and smaller fixed-blades. It's similar to the Gerber Gator except an older version that came with two Zytel sheaths; one for regular belt carry and the other for vertical, horizontal or chain-around-the-neck carry. Either sheath puts the belt at about the midpoint of the knife; most other fixed-blades I have put the belt at the top of the sheath, so you have almost the entire length of the knife banging against your leg. For urban carry, the Gerber is tops. Relatively short OAL, but thick-spined and scary sharp.