I have a couple of experiences of near-accidents - one I saw, and another I was involved in.
The first was a take-off at LGW in the 80's. I was on the observation deck, and a small airliner (?1-11/DC9) was starting to roll for a westerly take off. As I watched, a larger (but not a widebody) touched down just in front of the plane taking off. A few sharp intakes of breath from us spectators! If I remember correctly, the departing plane simply taxied around and took off properly straight away - I wonder what the pilot told the passengers caused the sudden braking.
The second was when I was taking an AF 727 from GVA to CDG. We took off heading east, and then turned north over the Jura mountains. Shortly after take off - still climbing (the ground was clearly visible below), and having made the turn north the plane took an incredibly sudden, steep climb, as we skimmed, all too closely, the top of the mountain range! Nothing was said and nobody else reacted - but I'm sure that the pilot had to take evasive action! I didn't have enough French to enquire as to whether that was normal!
Anyone else have similar stories?