HOLD R2, L1, Triangle, and Left and then press start to open a cheat menu.
Cheat Menu 2:
HOLD down R2, L1, Left, R3, and then hit Start to get another cheat menu.
Infinate Gold or Duplicated Items:
Have 2 players playing at the same time. You need to be in town for this. Then have one charachter drop all their stuff. Import the charachter that just dropped their items and they will have all the things that they just dropped but, it's also on the ground. Pick up all the stuff and sell the duplicates and save. You now have more money. Buy expensive items with your extra gold and repeat this cheat again. The more times you double your items the more gold you get each time. This also works with one player if you are at a save point.
Level 20 Charachter and 75000 Gold:
When in play mode, press L1, R2, Triangle, Left, R3 and start at the same time to instantly make your charachter 20th level, with 75000 gold, 1000 Health and 1000 Mana, and a minimum of 1 in every feat, including other charachter specific feats. The downside is that your charachter does NOT gain any further experiance points while playing, and is stuck at 20th level, with low level feats. The normal charachter max is 40th level.
Unlock Gauntlet Mode and Extreme Difficulty:
Beat the game on normal difficulty setting with any charachter to unlock The Gauntlet Mode. After defeating Gauntlet Mode you will open up the extreme difficulty level.
Play as Drizzt Do'Undren:
Choose 'new game' at the main menu, then hold R1+R2+L1+L2 while the game loads. Alternately, beat the game on Extreme difficulty.
Time Wrap:
Whenever you fight a big boss that gives you lots of experiance or you find a real good item, save before you find it and then when you get whatever you want save it on a different file. Reload the first one (before you got the item or experiance) and then just import your guy from the second game (the one just after you got the item).
Experiance and a Cool Sword:
Start a new game in extreme mode. Bring up the cheat menu (R2+L1+Triangle+left then hit start) turn on invulnerability and then level warp to the second to last towere level. Go down the stairs to the Black Forge, then walk east to the weaopn wrack and pick up the weapon then kill the metal golem who will drop the onyx sword. In extreme mode, if you were level one you should now be level 40. In other modes if you were one you should be level 25 or so. Also in the tower levels on extreme mode there are many chests containing powerful goodies. Remeber to keep invulnerability on.