Open up Combat Arena and set up the game as such: You need to pass Challenge of Olympus first. Note that this is an exploit, and may be patched with future updates to your Playstation 3™ There is a glitch where you can carry over your weapons and stuff to a new game. When the game asks if you'd like to switch difficulties, choose 'No.' Quit out and start a new game and you'll have all your weapons maxed out - even in Chaos Mode. Start the Arena on Titan difficulty and die a few times. (Unconfirmed) Beat all Challenges of Olympus to unlock the Combat Arena.
