Dynasty Warriors 8 Xtreme Legends - Pang Tong's 5th Weapon

 I think it's easy to get. This game and the older versions are easy in unlocking special weapon.

Though, I usually play this game when I'm offline How to get: Pang Tong (5th Weapon) - Dynasty Warriors 8 - Xtreme Legends - Main objectives: Rush the castle in 5 minutes - Tips: kill Zhang Ren first, or your health will turn red - My Advise: if you have more HP and damage, kill all officers around the camp to raise the morale so your friends don't be easy to be killed