I was stargazing very high in the sky to the North, towards the big dipper when I realized I had been seeing various flashes in my peripheral vision and I decided to focus my attention on them. I saw a fast moving object flashing, with a fairly regular pattern of two flashes in less than a quarter second, then a gap of about three quarters of a second. After observing a first pair of flashes, I concluded that the object was a fast moving airplane. However, when the next pair of flashes began less than a second later, the object was moving in a completely different direction, perhaps about 135 degrees off from its original heading. It didn't seem possible for an airplane to turn so quickly and completely.
The flashing light continued this rapid darting behavior, changing its heading seemingly almost at random with each pair of flashes. After seeing each pair of flashes, I could roughly guess where the next would appear, but the position and particularly the heading would always surprise me somewhat when the next pair of flashes occurred. It gave the impression of a pinball being bounced rapidly around by bumpers.
Over the course of about 90 seconds, the object bounced its way to the West, and finally over to the Southern sky, where I lost it behind some trees. There was no sound at any time.
I watched the sky closely for about 30 minutes thereafter, and I spotted the light twice more, after roughly five minutes intervals. In both cases, I observed it near the big dipper where I had first seen it before, and in both cases I only had about 20 seconds to observe it before it went behind trees or my house. However, there was one amazing pair of flashes (again, separated by less than a quarter second) when the object performed a complete 180 degree reversal between the two flashes.
After that, I watched the sky with gradually decreasing attentiveness for about another hour, and I didn't see anything else of interest. There were commercial airplanes in the sky off to the South while I was observing the flashing object, but they had no apparent interactions with it.
My impression was that the object was high up and far away, but I cannot rule out the possibility that it may have been closer, though it must have been at least above tree level, since it regularly disappeared behind the trees.
As an amateur astronomer, I am highly familiar with the appearance and behavior of aircraft, satellites, and meteors in the night sky, and this phenomenon appeared to be none of these.