How to remove a seized bottom bracket from a titanium frame?
If you are absolutely positive you know the direction of the threads, then an air operated impact wrench will do wonders.  I'm amazed at the difference when I remove threaded rear cassettes from my single speed wheels.  Removal by hand requires a long breaker bar, and a second person to hold the wheel from spinning.  Impact wrench is brizzzppp and done.  Its much easier to hold the tools tight to the work piece this way.  With long breaker bar, that's not so easy.

Again you need to know which direction is which.  (thumbs up to Daniel R. Hicks)