Brave Blade and Chicken's Knife Side Quest (World 3)
Once you make it to World 3 and visit the Ancient Library/the pyramid in the desert you'll be able to swing by the town of Moore to collect one of the two better weapons in the game. In the southwestern portion of the town you'll find a building which is connected to the forest. You can enter the back of this building (look in my screen shot above for an idea of where this is and where to enter; I am just above the entrance) and travel south into the forest.
The forested area is a bit confusing since you can't see where you're going OR even where you need to go. When you hit one of the dead ends the clearing that you see in the screen shot below will literally appear and the NPC in purple will ask you to choose one of the two weapons in crates.
As you probably already could tell by the name of this page, the two weapons are Brave Blade and Chicken Knife. The Brave Blade starts out with 150 Attack Power and will drop Attack Power by 1 point for each battle you've fled throughout the game.
On the opposite side of the spectrum you have Chicken Knife which will increase in power for every battle that you flee. Chicken Knife starts out with less than 10 Attack Power but can grow to have a total of 127 Attack Power if you run from enough battles. Chicken Knife also comes with a +5 speed increase too... But it also has one giant downside, while holding the Chicken Knife you have a 25% chance to automatically run from battle when auto attacking. You can use abilities like XAttack or Mug to bypass the auto-running aspect.
You can choose which ever of the two weapons you'd like. I'd recommend the Brave Blade if you've run from very few battles and the Chicken Knife if you've ran from more battles than you can count. I hate the Chicken Blade for regular enemies due to the built in run away from battle trait. Even though it doesn't fire when using XAttack it's still frustrating for moments when you're on autopilot and just spamming X during battle.