Philadelphia probably has the worst law:
§10-820. Cutting Weapons in Public Places. 
Cutting Weapon. Any knife or other cutting instrument which can be used as a weapon that has a cutting edge similar to that of a knife. No tool or instrument commonly or ordinarily used in a trade, profession or calling shall be considered a cutting weapon while actually being used in the active exercise of that trade, profession or calling.
(2) Prohibited Conduct. No person shall use or possess any cutting weapon upon the public streets or upon any public property at any time.
(3) Penalty. The penalty for violation of this section shall be a fine of not less than three hundred (300) dollars and imprisonment of not less than ninety days.