My personal favorites are "gravity surges" and "solar flares". Was doing some spins one day, everything going well, the engine was happy, the plane was happy, everything was happy, so I went for one more rotation. Darn near made it, too except for that invisible gravity surge. You never see those until they show up in results.
Solar flares can affect radio waves, and I think visual distortion and possibly even brain waves, as well as loss of short term memory and who knows what else. Nasty stuff!