Yanderes should be able to have access to any weapon.

-Knives-

This is a very common Yandere tool, they have fast and accurate with this weapon, be cautious when your yandere has a knife

-Other Melee Weapons-

Bats can be used to a lot of damage, and be leave fatal injuries.

Butcher knives are most likely to be used for a high-level Yandere

Scissors are common but have a small damage... If they don't stab multiple times, or stab REALLY hard.

Their own fists, Yanderes don't really use their fists, unless they know how to fight, so yeah, be careful, brass knuckles may be in usage.

Hammers can do extreme amounts of damage, and can even break bones, which are necessities to survive with. 

Sledgehammers can do HELL amounts of damage and can kill you instantly.

Hooks can impale your arms, and yanderes will use it to make you their best decoration in their room.

Sickles can be used to slit throats as well and cause fatal injuries. 

A whip can be used for sexual activities and considered a dangerous weapon.

Brass/steel knuckles can be used to leave fatal injuries to the face, and a limb necessary to run away or fight back

Axes can be useful beheading and cutting off limbs.

Chainsaws can be used for the ultimate massacres, fortunately, Chainsaws take time to start up.

Katanas can be used to leave a fatal injury and are fast, fortunately, many lessons are required to learn to use it properly. 

Machetes can be used to cut a limb off and can leave very fatal injuries.

scythes are difficult to find and are considered a weapon not used to kill, but instead, drain blood.

-Guns-

It's rare to see a yandere with a gun, probably because it takes the fun out of killing. Yes, Yanderes have fun, killing. If a yandere has a gun in their hand, then be very careful.