I thought it was 2.75" for Boston. I know one of the other cities had a 3" law, but Boston was weird.
I treated myself to a Sypderco Sage (carbon fiber scales, plain edge) when I started commuting in years ago. Looks great still. Carry's very low in the pocket and almost invisible. Doesn't look military Scarry and didn't scare people when I occasionally used it around the office.
If it's below 2.5" now... (Sage is 2.70 ) I would carry a boker subcom. They cost like $20 and are pretty durable. I have one in every bag as a spare. Alternatively, Spyderco Dragonfly.
One of the cops doing a detail in Cambridge stopped me while walking by and asked to see the Sage once. Of course I'd been walking by his car every morning for two weeks at that point.
I did the boys out hold the blade thing for a moment but he didn't say thank you. Let him have it anyway and he opened the blade, held it up to his name tag to I guess measure the length, was about to hand it back, and then spent almost a minute just looking at it. I then asked if he wanted to see my LTC-A. He laughed and passed it back to me.
Asked what model the knife was and a few other questions. A few days later while I was walking by, he got out of his car, and waved a Spyderco box at me. Said his wife wouldn't let him go out to eat with her if he had his griptillia because it was too scary.
I like the benchmades a lot, and they are every bit worth it, though big. The delica 4 line and sage just fit me better and have never let me down. I also usually prefer back locks. (Sage and Booker's are the only liner locks I have in regular use.)
My delics need new belt clips now, so I needed a second knife and usually have a Gerber LeBear with me. It's my dedicated knife for camping and hiking and any work. If I'm going to be diving into a project or moving boxes, working on a car thing or getting dirty, it's what I grab. I've abused the hell out of it and will buy another from Walmart if it's lost.
It was my "I'm flying and can't check a bag but refuse to not work without a knife with me" purchase. I thought it was gonna crap and disposable, but it's been with me for ten years.
Knives I bought but moved out of regular use:
Kershaw Leek: extremely sexy. Well built. Not very grippy. Instantly stained when touched with salt water and still look icky. Blade edge grind is sharp, but not very good for serious work. I would carve delicately with it, but never try and hack through a half inch rope for example.
CRKT: don't like their liner locks at all. One had a funky flipper flap which never really worked right. They feel flimsier than they were originally. They got tossed in toolboxes for cutting tape or being trashed.
Smith and Wesson 2000 anniversary knife. Nice little folder and my first pocket knife. It's on my range bag where it stays.
Leatherman folder with the integrated flip out gated clip. Good solid knife, but heavy for the size. It's in the garage some where near a door and is sort of a toolbox knife.
Smith and Wesson with seat belt cutter and window breaker in every car somewhere secure..