Late one night playing World of Warcraft a few years ago, I discovered a safe zone in a tree just across the road from my main (balance druid) character's farm where I could kill other player's characters from without getting a scratch. I discovered it by accident, sort of, after I decided on a lark to try to gank a few players coming into the vendor area while perched on a branch in the tree. Perch ganking is one of my favorite pastimes in World of Warcraft because it confuses a lot of players as to where the attack is coming from. I figured I could take out four or five player's, tops, before they got wise and found a way to take my character down.
But after finally finding a place to perch near the crook of the tree's main branches, I started killing players as they arrived and soon discovered they were powerless to stop me or to attack me in retaliation. The first few never knew what hit them and did not return for more punishment, but eventually some players did come back for more and began grouping up with others to try to kill my character as a team. They came in many groups by the tens, twenties, thirties...but could not figure out a way to get me. A few players finally found out they could knock me out of the tree with certain spells or weapon blasts, but it was easy to quickly run across the road into my farmyard for safety after being knocked out of the tree before they could catch me out in the open. In the meantime, guard NPCs were hitting them relentlessly for trying to attack my character.
After a few minutes hiding out in my farmyard, I would leave it, fly back to the tree, take my perch and start killing new arrivals again. The screenshot above only shows a fraction of skeletons of those I killed (or guard NPCs killed) as skeletons disappeared over time during the spree.
I killed hundreds of toons that night and a few other nights after that. Eventually, though, someone complained to a game master and Blizzard fixed it so players could no longer perch in that tree and remain safe while attacking others.