One from Saturday sticks in my mind.
I was joining the M11 N from the M25 W, and it's a wonderful piece of sliproad if you know it. Came round it at a decent but sensible speed (well within the limit), no traffic near me so indicated to join the M11 and started to accelerate up to NSL. As I did so I noticed that there was a slow moving pick up truck also about to join, who was not indicating. I checked my mirrors, and my blind spot, and decided it would be safer to proceed straight to lane 3 in case the pickup decided to jump straight to lane 2. Did so after indicating, then realised there was a white TT already in lane 3.
He was a fair way back and travelling at approx the same speed as me, and I'd like to think that I subconsciously saw him and decided to make the move anyway as there was plenty of space (he didn't have to brake at all), but I do not remember doing that on purpose. It's not impossible that I just didn't see him, and it could've appeared that I was being a numpty and pulling straight into lane 3 for no reason. I genuinely don't know if I saw him or not though, and that's very frustrating for me as I've worked very hard over the years on my observation as it was one thing I felt needed improvement as a young driver.
No accident, not even close really, but it's reminded me again that I'm not as perfect as I would like to believe. Still better than 99% of other motorway users who seem unable to grasp the concept of keeping left, though!