Philippine Ragnarok Online has been around since June of 2003. It has become one of the most well known MMORPG's in the country with more than an estimated 12,000 characters in-game at any given time. With such high populations, the game attracts undesirables just like any other highly populated areas; such as malls and parks. Being undesirables they have insidious and often ingenious plots to cheat players out of their hard earned equipment or cash.
The Switcharoo Edit
Quite common in the older days of pRO, it begins with the undesirable advertising to buy or sell certain items at a certain price. Usually buying at incredibly high prices or selling at rock bottom rates. The victim would then deal the undesirable and either punches in the zenny value or places his items into the deal dialogue. The undesirable would then purposefully put a different item or the wrong zenny amount into his end of the deal.
For example, the undesirable might advertise to be selling Trunks. When the victim deals the undesirable, the undesirable would put Barren Trunks or any of the two other Trunk look-a-likes into the deal dialogue. This style of scamming has led many to ask the "vendor" to use the Merchant skill Vend, instead of using the deal dialogue.
Ghost Deal / Vanishing ItemsEdit
A rather old scam method that exploits bugged game code. This scam usually fronts a "Can I see the description of your headgear?" statement from the undesirable. The undesirable would then sweet talk the victim into "holding" some items for him to transfer to another account, using the currently open deal dialogue. During the deal dialogue the victim's item/s would suddenly disappear, giving the appearance of an empty deal dialogue with only the undesirable's disposable items. The victim's item/s are still there masked by the buggy game code. Continuing with the trade would swindle the victim of his items. Cancellation of the deal will return items to their correct owners.
Using a new feature of episode 18 (Demise of Morroc) is a good counter measure to this kind of deal. In your equipment window (ALT+Q) there is an option on the lower left corner to enable any player to take a look at your current equipment and their descriptions.
The Force Deal Edit
A truly insidious scam, this causes the deal dialogue to become unterminable and whatever items or zenny already in the deal dialogue will go to the undesirable. Rumor has it there is a third party program that makes this possible. Exiting the game in any way will cause the deal to continue business as usual. The only known way of getting out of the deal is to have someone else deal you and then terminate that deal dialogue. This type of scam is only applicable when it's the scammer that deals the victim. It's best to have /notrade on to prevent such scams.
The Impersonator Edit
The undesirable would send you a private message saying they are one of those characters you helped out long ago, who you conveniently have forgotten. He would then present "proofs" of your acquaintance and proceed to sweet talk you into lending him some items which you will never see again. Undesirables also like to impersonate famous guild masters or vanguards and would go as far as to ask for your account details.
The Space Scam Edit
This scam also uses some bugged game code. Creating a new character whose name starts out with a ridiculous number of spaces, the undesirable would then append the name of a vanguard. Using this format of a name, the undesirable would be able to join chat rooms and will appear to have a legitimate name when they talk. But looking at the chat list there is no additional name. The undesirable would then use cajoling to get you to deal items to an accomplice who has also entered the chat room.
Only Two Garments at a Time Edit
This scam like The Impersonator works by borrowing items and running away with them. It is started by the undesirable wanting to see if the headgear you are wearing will look good on their character. This is of course a rouse to swindle you out of an expensive piece of equipment.
It Takes Two to Tango Edit
As the name suggest this scam technique uses two characters. It may be two users or just one user using a bot.
The most common variant of this scam is where one character is advertising to buy an item, usually quest or recipe items, at an exorbitant price. The other character would then be somewhere else in the market place selling the item (via Merchant skill Vend) that is advertised at slightly higher than market value. The plan of the undesirable is to lure people into a seemingly lucrative buy and sell deal. However as soon as there is a major purchase with the character selling the items the character buying the items would then disappear. Leaving the victim with a cart load of useless (may be useless for the victim) items. The victim would then proceed to rush sell the items at cheaper than market value to try and recover his losses.
Another, more complex, angle to this involves a victim that is advertising to buy a certain item of great value. One undesirable would position himself close to the victim with an advertisement to trade another item with the item the victim is looking for. The other undesirable would then position himself also close to the victim but would be invisible (outside the screen) of undesirable A.
victim's ad: B>+10 Valkyrie Helm 
undesirable A's ad: T>+10 Valkyrie Helm  for +7 Coat 
undesirable B's ad: S>+7 Coat  RUSH!!!
The victim, being able to see both ads would then be lured into a seemingly lucrative buy and sell deal. As soon as the victim buys undesirable B's item (at usually higher than market value), undesirable A would then disappear, leaving the victim with an unneeded piece of equipment that cannot be sold at the original purchase price.