The air cannons shot pumpkins the furthest. Each cannon has some sort of tank that is pressurized. The more pressure... the greater the distance (assuming the pumpkin comes out of the end of the cannon in one piece.) For the final shot one of the cannons pressurized to 200 lbs/sq inch. Their pumpkin shot well over 4000 feet!
The National competition was halted and was not aired recently when a woman was hit by a piece of metal from an air cannon. From more recent reports it appears that the woman, a journalist, will be OK and she is sad that the competition was stopped.