I was just there. I don't know about knives. I had a leatherman micra with me, but that was it.
Check out the "Old City" I think they call it. It's pretty cool to go at night. Be prepared to be surprised when it comes to food. The food tended to be a little weird (for my tastes), and the portions were very very small (here in America we're definitely used to larger meals than the rest of the world! - I never really understood that until I started traveling internationally).
The bus tour is pretty neat to do on the first day as it will give you a better idea of what you want to do while there.
The Asian district/Chinatown is really freaking weird and didn't seem safe IMO.
Check out the olympic dorms (Now a condo building) as you'll recognize it from movies along with the wireframe globe thingy (kind of like a wireframe version of the Epcot Center globe) that is across the water from the dorms. Also, their stadium is pretty cool. The science museum is neat too. Expect mimes and jugglers. There were a lot of them (I didn't mind since I'm a hobbiest juggler).
That's most of what I remember. I was only there for 3 days or so though. Oh yeah, if you like art, the Art Museum is actually very nice, possibly even better than my two favorite art museums (Cleveland and Boston MFA)
I may have been breaking the law with my little Leatherman, but I didn't think about it until I was already there. If you go to a gun store there, take a pic as I'd love to see what they look like and carry. I should have visited but I didn't.