Under texture "exploit"

Not even sure if you can call this an exploit but oh well, searched for roughly 20m to see if this was a repost and couldn't find anything related to this one so I'm just going to post it.

You need two accounts or a friend with a passenger mount to help you out. Char A mounts up on a passenger mount and starts running into a wall. Char B jumps up on the passenger mount. Char A now simply logouts (the character must be logged off instantly or it won't work - so use it in a city) and char B will now go through the wall. 

This can be used to either disconnect other players (if they fall too much) or just explore stuff.