I think it would open up a huge new dimension of creativity in Second Life if gravity could be manipulated. Presently gravity only applies in a downward direction, but imagine the possibilities if gravity could be applied to various selected surfaces, such as walls etc.
The link below is to something I built in Second Life a few years ago, and as you can see not all floor surfaces are downward facing. Whilst visitors exploring this build could use a wall walker script to walk on different surfaces this had many limitations. For example, if someone sat on a chair in certain rooms then stood up, they would fall downwards because the wall walker could not be active whilst the sit script was active. Also its not possible to limit what a wall walker script allows an avatar to walk on.
There are many games that use this manipulation of gravity. Examples include Manifold Garden, Nomori, and Etherborn, (the image is from the latter game). All of these and more demonstrate gravity manipulation is possible and can lead to some very imaginative and innovative creations.
This link is to the Etherborn promo video that shows just one example of a what manipulating gravity feature could do: