I remember I used to be so stressed after reading threads like this thinking that my next trip would just be a huge battle with rude people, line cutters and parade pushers
I've had a couple of experiences with other guests doing annoying - or strange - things, nothing that would ruin a day but certainly things that have me going
One of my pet peeves is people using their phones during rides/attractions. One day we had a woman sitting in front of us on the front row at the Enchanted Tiki Room - she was on her phone, checking Facebook, for the entire duration of the show. Since she was on the front row, we couldn't help getting distracted by the light from her phone. On the same day we were behind a man on POTC who had a telephone conversation with someone the whole time we were on the ride. It was irritating but not a disaster - we just went right back on again - but I couldn't understand why he would bother going on the ride at all. Impressive signal, though!
The other thing I find annoying is people reciting the spiel in Haunted Mansion, Tower of Terror etc. Attention seeking at its worse - we get it, you've been on the ride before, but there are also people who haven't and you're not half as entertaining to those people as you think you are