Pike

This weapon is meant to be used to deal greater damage to mounts that charge into them. Instead of taking the attack action or ready action, you may use your action to set your spear. When a mounted creature moves towards you and enters your reach, you may use your reaction to make an attack against its mount. This attack is automatically treated like a critical hit if it lands, regardless of the actual roll. If this kills the mount, the rider must make a DC13 Dex saving throw or be pinned beneath the mount when it collapses. 

This weapon adds 5 feet to your reach when you attack with it.