An improvised weapon is an item which was generally designed to be used for other purposes, such as farming, gardening, or playing sports. While the intended use of these items is not for the purposes of harming others, the way that they are made, and what they can do, means that some people will use them to cause harm to others.
The Baseball Bat and its cousins, like the Softball bat, and the Cricket bat, are used for fun and games, and rarely cost more than thirty dollars (or equivelent), and, with a few exceptions, require no paperwork to own. Most people have one in their homes. While they are made to send balls flying, they can also smash skulls.
The Machete and its cousins, like the Cane Knife, the Bolo Knife, and the Kukri are also quite common, especially in agricultural areas. While typically used to cut down small trees, chop up food, and cut down sugar cane, their blades can be used for hacking and slashing.
Generally, most modern troops are issued something along the lines of an E-Tool, so that they can dig a foxhole. Sometimes, soldiers will have one of the edges sharpened, so that they can hack through roots with ease. If a soldier were to be caught without their gun, they can grab their E-Tool and use it like a battleaxe, and do some damage. This tactic is also effective during close quarter combat, and often times, soldiers are trained to use them for this purpose.
The lasso is an item that many nomadic people had with them, so that they could catch livestock or wild animals. This can also be done with people, whether it be to save a fellow warrior, or to strangle an enemy.
Somali Pirates often carry a grappling hook with them to hook onto passing ships and climb aboard to raid them, but in a pinch they can use it to defend themselves at close range by swiping its barbs at an aggressor.