Guisarme

Natural attacks with this trait can be used to attack creatures up to the listed distance away instead of only adjacent creatures. Weapons with this trait are long and can be used to attack creatures up to 10 feet away instead of only adjacent creatures. For creatures that already have reach with the limb or limbs that wield the weapon, the weapon increases their reach by 5 feet.

You can use this weapon to Trip with the Athletics skill even if you don't have a free hand. This uses the weapon's reach (if different from your own) and adds the weapon's item bonus to attack rolls as an item bonus to the Athletics check. If you critically fail a check to Trip using the weapon, you can drop the weapon to take the effects of a failure instead of a critical failure.