*6/18/09 UPDATE: Using this method will change your weapon type and will prevent abilities that require a certain weapon type to be used. Example: Mutilate
*10/24/10 Update: Wow no longer uses Itemcache.wdb.
Program needed: Freeware Hex Editor XVI32 or any hex editor
1. To start out open Worldofwarcraft\Cache\ADB\enUS\item.ADB with your hex editor and minimize.
2. Open your internet browser, go to wow.allakhazam.com, do a search for your weapon (I'll use Thunderfury, Blessed Blade of the Windseeker), and click on it. Now click xml on the right side where it lists the buy/sell price of the item. Scroll down until you find <displayinfo>30606</displayinfo> copy that number (30606) into a dec->hex converter. I used http://www.parkenet.com/apl/HexDecConverter.html.
3. Now take the hexadecimal which should be 778E and switch them around to 8E77
4. Now restore your hex editor and hit CTRL + F and put 8E77 as a hex string not a text string. Hit ok.
6. You should see 4x[FF] ([FF][FF][FF][FF] <--- like this to the left of where your cursor is) now follow this line left until you get to the first box with a value (other than 0 of course) in it and in my example (Thunderfury, Blessed Blade of the Windseeker) that value is a [07]
7. Now you know the Itemid=8E77 and Item type=07
8. So now search for the item your character has equipped and replace the Itemid and Item type with the numbers you found on step 7
9. Save, log in and enjoy
I'll list some Item types now to save you some trouble
Dagger: 0F
Fist: 0D
?Fishing Pole?: 14
Thrown: 10
Wand: 13
1h mace: 04
2h Axe: 01
Polearm: 06