The following is my stance on many items that define my belief of legit Diablo play:(not finished yet)
Abuse of bugs: I oppose the use of bug exploitation in Diablo. If you use the duping bug, anti-stun bug(having hit points less than character level and use of mana shield) or trap Butcher in the stairs bug, I don't consider you a legit player.
Character backup and restore: I believe you should be allowed to backup and restore your characters. The only acceptable time to restore, is after a technical problem, i.e.: lag out of game with items on ground or loss of char on system due to any of various reasons.
Godly Full Plate does not exist in any public version of Diablo. If you have one, it is a hacked item. Holy full plate does not exist in Diablo. Use logic on this issue. You do not need to consult Blizzard or Jarulf on this matter. All of the Godly full plates that i have seen on bnet, were near perfect in stats. AC 73 or above, +195% armor or more and +96-100 hit points. I have never seen a Godly fullplate with stats such as this: AC63, +178% armor and +84 hit points. I feel the reason for this, is that if they are going to make a hack, they make it nearly perfect. Also, if GPOW were ever available, then HPOW would also have been available and much easier to buy or find, yet, I have never seen a HPOW on bnet. Godly and Holy items cannot be dropped by any monster in any version of Diablo, the quality level for those prefixes are too high. Godly or Holy Full Plates of any kind cannot be bought from Wirt due to price restrictions. Griz cannot sell items of Godly or Holy quality in any version, due to quality and price restrictions.
Other common hacked items: Dreamflange(as anything other than a mace), Thinking Cap (as anything other than a helm),
Outside (third-party) programs:
I feel that the use of third-party programs are acceptable as long as they do not give you an advantage over other players or over the monsters in the game. You should rely upon your own skills to defeat any opponents. These tools like any other can be abused, please use wisely or not at all.
DiabloSaver: I use this program for a few things. The main use is to scan other players to check for dupes, ears, hacks etc. it is not perfect and a good dose of Diablo knowledge is helpful in noticing the minor mistakes that it will make. I also use it to occasionally backup my characters. (more on my beliefs on backups in another section) I also use this program to enable the play from Hard Drive hack, the reason that I use this hack, is because I have purchased 3 Diablo CD's thus far and my third one is getting severely scratched (my Diablo CD seems to be smaller than other CD's and rubs on surface of the tray) I have supported Blizzard with the purchase of 3 copies of Diablo... I think that is enough and will save my money for DiabloII when it is released. This program also allows for conversion of single player character to multiplayer characters, this is a feature I disagree with and will not use or recommend. There are a few other features of the program, that I will not mention do to my lack of knowledge on them and lack of use.
DiabloSight: This is similar to DiabloSaver, but it can only scan your character and others to verify item and character status. I recommend it to all who play public games. Please read the readme file included.. this program is not perfect.
DiabloBackup: This program works outside of Diablo and will make a backup copy of your character files. I relied upon it to safeguard my characters once upon a time. But, I had to reformat my hard drive a while ago, and when I tried to restore my characters.. it was unsuccessful. Others have had no problems, but I will rely upon other methods to backup my characters.
Trainers: Stu's, Raymond's, Bobafett's and others. These programs can be used to backup your characters. They can also be used to enable many cheats. I will not cover those, as I have little knowledge of them. I regard these programs as programs to gain an advantage over other players or monsters and will not recommend the use of them.
DiabloHack: This is another program used to enable cheats. But it does have one or two redeeming abilities. You may also use this program to enable play from hard drive, if you have worn out your CD like I have:) Also you need this to play mods on bnet (more on mod play next.)
Diablo and HellFire mods: These are hacked versions of Diablo or HellFire. If used properly I feel they are a great way to further your enjoyment of these classic games. I fully support the playing of mods, as long as you treat them as a separate game!!! Do not attempt to game with others using regular Diablo while using a mod, you may make the game crash or other problems may arise. Do not attempt to import items from mods, these items are different and belong only in the mod!!!