Jus a few:
1) On our first trip to WDW we stayed at the Boardwalk and our first park was Epcot. We went there in the late afternoon on arrival and entered through the International Gateway. This is a very underwhelming way to enter your first WDW park and lacks the grandeur of the front entrances of other parks. Honestly, I think everyone should go to MK first on their first trip. No greater welcome than Main Street.
2) We were there when Hurricane Jeanne approached. We knew it was coming Sunday but assumed since we flew out Saturday we'd be beating it and we'd miss it. Stupid. We got back to our room after a fab dinner at V/As Friday night and discovered the airport would close early Saturday. We couldn't switch flights. We had to stay two extra nights which was expensive. (Although I can't say I entirely regret this mistake... it was expensive and temporarily stressful while we were trying to decide what to do, once we resigned ourself to staying we had a great time. The day we spent confined in the room was a much needed relaxation day at the end of our vacation!

)
3) Never leave a man behiind. My dd and I had a great mother daughter trip once (before she had a brother.) My dh rarely shows interest in planning a Disney trip and was buried in work. We had the opportunity in the middle of the winter for a quick getaway and I proposed it to him but he was swamped, but encouraged us to go, thinking he could get some work done while we were gone. He was totally okay with us going. Then two days before we left he got depressed. I wanted to priceline him an airplane ticket to join us but he refused. He was really sorry to be missing out We had a great trip but felt really bad we did it without him. Now that we have done WDW a few times I remember that dh only gets excited about the trip about 24 hours before we leave and not to worry about it one way or the other. But we're never going without him again.
4) When my dd was barely 4 we took her to It's Tough to be a Bug. On the way in we ran into a familyexiting the attraction with a little boy about 5 bawling, I mean, really panicked and hysterical, although his sibling seemed fine. Stupidly, I asked the mother, "Do you think this attraction is okay for my daughter?"
"It's great!" she told me. "We loved it. I'm sure it's fine. He's just...." she said, indicating her son with a shrug, as if to indicate her son was a werid egg.
So we went in, my daughter was completely hysterical by halfway through the movie, and we couldn't get her to sit down in any theatre-type attraction again for the rest of the trip (this was day 2 of 7.) D'oh!
This is just a few. I'm sure I have more!!!