Over the ages there have been many accounts of ball lightning.
Some accounts from Wikipedia are as follows:
One of the earliest descriptions was reported during The Great Thunderstorm at a church in Widecombe-in-the-Moor, Devon, in England, on 21 October 1638. Four people died and approximately 60 were injured when, during a severe storm, an 8-foot (2.4 m) ball of fire was described as striking and entering the church, nearly destroying it. Large stones from the church walls were hurled into the ground and through large wooden beams. The ball of fire allegedly smashed the pews and many windows, and filled the church with a foul sulfurous odor and dark, thick smoke.
The ball of fire reportedly divided into two segments, one exiting through a window by smashing it open, the other disappearing somewhere inside the church. The explanation at the time, because of the fire and sulfur smell, was that the ball of fire was "the devil" or the "flames of hell". Later, some blamed the entire incident on two people who had been playing cards in the pew during the sermon, thereby incurring God's wrath.
One without a religious angle:
In 1954 Domokos Tar, a physicist, observed a lightning strike during a heavy thunderstorm. A single bush was flattened in the wind. Some seconds later a speedy rotating ring (cylinder) appeared in the shape of a wreath. The ring was about 5 m away from the lightning impact point. The ring's plane was perpendicular to the ground and in full view of the observer. The outer/inner diameters were about 60/30 cm. The ring rotated quickly about 80 cm above the ground. It was composed of wet leaves and dirt and rotated counter clockwise. After seconds the ring became self-illuminated turning increasingly red, then orange, yellow and finally white. The ring (cylinder) at the outside was similar to a sparkler. In spite of the rain, many electrical high voltage discharges could be seen. After some seconds , the ring suddenly disappeared and simultaneously the Ball Lightning appeared in the middle. Initially the ball had only one tail and it rotated in the same direction as the ring. It was homogenous and showed no transparency. In the first moment the ball hovered motionless, but then began to move forward on the same line with a constant speed of about 1m/sec. It was stable and travelled at the same height in spite of the heavy rain and strong wind. After moving about 10 m it suddenly disappeared without any noise.
There are also videos purporting to be ball lightning available on YouTube and I have heard a hypothesis that this UFO incident could be ball lightning.
So the question remains is ball lightning scientifically verifiable, or is there another explanation for all these events (e.g. meteorites, imaginative stories, video manipulation, etc).