Pretty interesting little (or big even) exploit I found here.
Was doing a bit of exploring and at one point I needed a slowfall buff, being on my Warrior I decided to use the Hallow's End Pumpkin Treat buff that turns you into a ghost (OoOoOoo...).
To my surprise you can easily do some old school wall-walking with this buff, literally just go to a mountain, find an edge that's to steep, and walk along it.
Here's a screenshot of me stopped mid-mountain -
http://img227.imageshack.us/img227/3854/hallowoah.png
Obviously this is really only going to be useable during Hallow's End (unless the Priest levitate spell is effected, which I doubt but will check out) so have fun with it while you can!