Minecraft wiki entry for Weapon, associated text: End Crystals and Respawn Anchors can be used to deal excessive explosive damage to targets in quick succession.
Cobwebs can be used to drastically slow the move speed of targets.
Flint and Steels and Fire Charges can be used to set the ground on fire and damage enemies.
A Lava Bucket can deal serious damage to enemies and significantly slow them down, but it requires strategic placing. In certain situations, it can be used in conjunction with a Water Bucket to suffocate the entity in Obsidian.
TNT is an effective weapon against enemies, whether planted and ignited on the spot or buried beforehand and activated in a chase. The player can substitute this with a TNT Minecart, Creeper, or a Bed when used outside of the Overworld.
Hostile mobs can be used as weapons when used strategically, but this can be hard to set up due to the fact that these mobs also attempt to attack the player.
Redstone traps can be used to kill the entity with all sorts of environmental damage, ranging from fall damage to suffocation to anything in between, but these must be prepared beforehand.
Anvils can be used to damage mobs and players, at the cost of damaging the anvil.
Certain blocks cause damage on contact, and can be used as barriers to mobs and players without the ability to break blocks. These include a Cactus, an Sweet Berry Bush, a Wither Rose, a Campfire and Magma Block (if the target isn't sneaking or wearing frost walker boots).