Walking home the other night, listening to
Sleep's cover of Snowblind, and thinking about
Order of the Stick and
Table Titans, I had a D&D idea.
Planeshift/alternate D&D world, where all monster alignments are Good/Evil reversed. It's probably been done before, but I think it would be interesting. Good orcs! Evil elves (except the Drow)! It's a little harder to apply to classes, though -- I can imagine Lawful Evil Paladins, but Good Assassins? Might just keep class alignments intact.
I thought about reversing Law/Chaos as well, but that makes less sense. It's easier to keep that as-is.