Standardly stuck:
Get three guys per side, twist in opposite directions and bingo.
Really stuck:
Support on both ends, bounce on it, turn 90 degrees, bounce, try to twist it apart.
Utterly stuck:
Make up an adapter to force mains pressure water down the top of the mast (remove the top bung first). Shake the mast while drinking beer. It normally takes two or three beers before the mast separates.
1 piece mast:
Tie one end to a solid tree using a "prusik hitch" (
en.wikipedia.org/wiki/Prusik_knot), tie the other end to your car's towball. Rev and go!
Next time you rig up:
Wrap the joint with electrical tape, this stops sand getting into the gap that a bent mast has between the ferrule and mast at the front of the mast.