Achron a new RTS in development is cool in that it is a 4D RTS. Yes, time is now an element in this game where you can go back in time and then changes back in time are propogated to the present.

http://achrongame.com/site/index.php

The graphics are kinda blah, but the whole concept of using time as an element is at least kinda fresh. I know using time and rewind features in Braid and Toki Tori have been there for awhile, but this seems a bit more ambitious.