.hack Part 2: Mutation Cheats

After beating the game (or maybe before i did this after) Go back to the
first root town and visit Haunted   "Forbidden  
Holy Ground" four times. Each time you see a special cut scene from
the show .Hack//Sign. You also get a special Key Item And a Gold or
Silver Grunty thatwill increase you health and magic.

If you Data Drain monsters, you can either get Virus Cores or weapons/armor. Most high level monsters have very rare weapons and strong armor. Most of these monsters are above level 45; be careful when fighting them. If you do not receive the item, keep Data Draining that monster. However, do not Data Drain too much where you are in danger of system crashing:

Your Grunty will often have good weapons, try to find him and make a trade.
Although you will be lucky to get any rare weapons from your Grunty