When the omelet station is holding up the line, and I am trying to get some food in me before a tour or something, I will ask the people waiting if they are getting omelettes. If they say yes, I keep moving down the line and usually end up skipping ahead. But, the key, I think, is doing it with courtesy. Asking if it is okay usually gets me there. The same if I forgot to get something. A polite request always works....well, almost always, there is the occasional grump.
I did cut in line once. It was on NCL and I was out on deck and noticed dense smoke coming out of one of the ship's metal ashtrays. I went inside and went to the purser, where there was a long line. I went to the desk and tried to discreetly inform them of the situation. The purser I was dealing with told me I had to get in line. I replied that if she did not consider what might turn out to be a fire as high priority, she should find another occupation. She then said she had misunderstood me and took care of it. I apologized to the man who had been talking to her and he was very polite and said he appreciated my doing what needed to be done. As it turns out, the NCL "butt bins" cannot spread fire even if flaming, but I didn't know. I only knew that fire at sea is a big problem.
The point of all of this is just that sometimes taking a moment to explain ourselves and/or apologize even when our actions are justified can go a long way toward developing civility.