With exceptions for the elderly, pregnant, and the disabled, I get annoyed by people cutting in line. Earlier today, I fell in line to buy lottery tickets (don't ask me for lucky numbers - the most I got correct was 3). I actually took a bit of time to fix the line somewhat because it wasn't immediately clear where the end was, but everyone in front of me were pleasant, and we even made small banter about hoping some luck fall our way.
So far, so good. As soon as the guy in front of me finished buying his ticket, some jerk of a lady suddenly slid her lottery picks in front of me, and the sales clerk, who just turned around after putting the previous guy's money in the cash drawer, mistakenly took the jerk's ticket, thinking it was mine and started to process it.
