Many sound related issues, forcing players to disable sound during raids.
If the entire group leaves a Heroic instance, even for a few seconds, the instance will reset, unless a boss has been killed. This can even cause instances to be unenterable (i.e. if you try to exit and enter an instance 6 times an hour, you will be unable to.)
NPC-Item: - Using the whistle that the Cenarion Outlanders provide you for aiding you will allow you to attack a player of the opposite faction in Zangarmarsh. If this player attacks back they lose 125 Rep points with that Faction.
Quest: - "Return to the Abyssal Shelf" in Outland Horde side, reports of players being stuck on the Wind Runner and unable to dismount without the aid of a Game Master.
Terrain - Jumping against a flat surface with your right foot on the wall will cause the player to clip the plane, allowing scaling of mountains and other terrain. Players are now calling this the new way to Wall Walk.
NPC-PvP: -Sometimes getting hit by guards in Nagrand will cause you to become PvP flagged, even if you perform no hostile actions against them.
PvP: - During a duel, Priest are able to kill themselves as well as their opponent while a DOT is active on the target, and the Priests health cannot sustain a hit to Shadow Word: Death.