Here's one I used just to confuse the hell out of people:

You enter a hallway from a door placed at one end of the hallway, on the left side. In the center of the hallway, there is a white line. There is a similar type of line surrounding the door at the end, which is on the right side.

When you cross the line in the center of the room, you are teleported back to the door you entered from. If, one way or another, you manage to get past it and to the end of the room, and open the door at the end, you'll see precisely the same hallway before you.

You cannot detect any teleportation magic anywhere in the room, and while dispelling may work on the center teleportation trap, it does not seem to work on the second.

Solution:
Spoiler
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There's only one teleportation trap. While you are indeed teleported when you reach the center of the hallway, when you reach the door at the end of the hallway, it just leads into another identical hallway. This repeats about ten times.

So really, get past this puzzle is very simple. You just have to keep walking- the thing is, it tends to mess with people's heads so that they stop and puzzle over it and bog themselves down.

If you feel extra mean, make it so that there is a second spell over the hallway group that makes each hallway mimic the appearance of each other hallway, no matter what is done to them.