At 17000', 747 descending into BDA in heavy cloud, a stream of not brilliant lighning appeared coming through the cloud dead ahead streaming straight to the aeroplane. It must have lasted about 6 seconds or more. We had that funny atmosphere you get- our hair was standing on end because we were really scared- it looked at if it was heading straight between each of our knees. Ended with a very big flash and bang. I simultaneously felt something like a flick on my watch, which was new and rather expensive, but undamaged. That was one of the unusual strikes. Lots of flashes and bangs and holes made, but the scary stories are the ones about ball lightning appearing in the cabin and wandering about for many seconds. Still nobody knows anything about them. A prize for the first guy with the guts to stick a finger in one!