Perhaps the perfect solution?

[Efflixi Aduro]

Well, I started playing a game called mu and i got the idea from there.
As many people want open pk i thought this would solve it.
If somone kills another person twice then they become a Killer. A killer wont be able to purachase anything from merchants because they will run away. Won\'t be able to get into citys because they will get jkilled by the gaurds. And if another player Pk\'s a killer they wont be called a killer.  A killer could do a few things to lose the tag. Kill X amount of killers to become normal again, kill x amount of monsters, or if they ar on for X hours they will be nomal again. This could be adjusted so i won\'t say much. What do you guys think?

[Nonk]

Nice idea, it would add a certain element of danger when travelling from one town to the next, and make the profession of guard more feasible.

[WizardsRule]

what would you gain from killing. Half loot, entire loot, what.  It seems like a lot of punishment for just a little crime.  I think that you can enter a city but be prepared to fight off the gaurds.(kinda like .hack\\\\sign)

[Brinley Cassidy]

I think it\'s a good idea. Maybe the punishment is a bit too severe (seeing as how many, many people want to PK), so maybe it could be something like, \"Oh, you killed X many people, we\'re fining you X amount of money.\" The fine would depend on the player\'s level, so if you killed a newbie, you\'d be fined more than if you killed someone one level under you.

But there would have to be a way to determine if you PKed, or if you were defending yourself.

[derwoodly]

Perfect solution? Did you read any of the other threads in this section?

This one has been sugested before.  Pks will just stay out of the city and kill newbies all day long.  They wont care about merchants running and guards attacking them.  

What is preventing some high level players from wiping out an entire town?

[wormking]

money getting taken directly from the bank (once there is a bank) because of too much PKing

Or lots of super-strong guards would attack you.

[Cyberchu]

The bank and fine ideas would not work because the Pker could give all his money/loot to an alt/friend to store/sell it. Also if these guards are unbeatable it will detract some realism from the game, if they are not invinsible then someone of high enough level could kill them. It\'s a dilema.

[derwoodly]

Nods in agreement with Cyberchu,

The rules would apply to pkers and anti-pkers.  When hunting down known bad guys, all of the murder flags would be put on you as well.

Lets assume you see a \"bad guy\" kill a low level player and rob him then log off.  Thus preventing you from attacking him right away.  You being the \"good guy\" happen see the same bad guy a week later and want to pay him back.  By this time his pk status is gone.  Now if you kill him you will be marked and have money taken from your bank and chased by the guards and any other punishment the games dev have put in.

[ajdaha]

It should all depend on wether anyone sees you. If an NPC sees you, depending on the NPC you will probuably be found out, and you can be punished. If a PC sees you then if that PC reaches an NPC you are punished. You should try to kick that PCs ass or bribe him to forget what you have done before he reaches the town.NPC.
That just came out of my mind but is better than half of the over-used ideas on these boards.
Common planeshift, be original

[leuxast]

The gaurds would have to be PC\'s not NPC\'s because the NPC\'s would have to be super complex.