I sometimes keep an expandable baton with me.
A billy in CA, a felony just to have in the state, nevermined on college campuses.
A felony, called a blackjack or sap. Possession of a deadly weapon.
One of my favorites for improvised weapons is two socks (one inside the other) filled with change... to quote some one here "it ain't tacticool, but one good hit and its coloring books for X-Mass from now on"
Known as a sap, sandclub, sandbag, both felonies under possession of deadly weapon law in CA.
You can take the Wildcat with you anywhere.
Metal knuckles of any type are banned in CA and perhaps they would not be identified, but if caught they are specificly outlawed.
another billy, with no none weapon use banned as possession of a deadly weapon.
Here is one law in CA that covers all of those, though there are many additional weapons laws, particularly concering places of education, and specific types of weapons like knife variations, assault weapons, etc:
12020. (a) Any person in this state who does any of the following is punishable by imprisonment in a county jail not exceeding one year or in the state prison:
(1) Manufactures or causes to be manufactured, imports into the state, keeps for sale, or offers or exposes for sale, or who gives, lends, or possesses any cane gun or wallet gun, any undetectable firearm, any firearm which is not immediately recognizable as a firearm, any camouflaging firearm container, any ammunition which contains or consists of any flechette dart, any bullet containing or carrying an explosive agent, any ballistic knife, any multiburst trigger activator, any nunchaku, any short-barreled shotgun, any short-barreled rifle, any metal knuckles, any belt buckle knife, any leaded cane, any zip gun, any shuriken, any unconventional pistol, any lipstick case knife, any cane sword, any shobi-zue, any air gauge knife, any writing pen knife, any metal military practice handgrenade or metal replica handgrenade, or any instrument or weapon of the kind commonly known as a blackjack, slungshot, billy, sandclub, sap, or sandbag.
(2) Commencing January 1, 2000, manufactures or causes to be manufactured, imports into the state, keeps for sale, or offers or exposes for sale, or who gives, or lends, any large-capacity magazine.
(3) Carries concealed upon his or her person any explosive substance, other than fixed ammunition.
(4) Carries concealed upon his or her person any dirk or dagger.
Many things like "leaded cane" apply to anything with intentionaly increased weight, lead or other substance. Things like "billy" apply to any blunt weapon without a legit non weapon use that warrants you having it. Sap and sandbag can include anything, even a purse used as a weapon if filled with heavy objects, nevermined an object intentionaly made for the purpose.
Also most objects if intended for use as a weapon fall into one of these catagories if you are asked it's purpose and reply that it is "for self defense". That implies intent and makes it a weapon. A baseball bat for example if kept for self defense would be a "billy" while having it around because you use it for recreation on occasion does not make it a billy.