If its appropriate, for example if I have a long queue behind me its really entitled to think I can make the decision for the queue. If its just me then more often than not I will wave someone in front of me.
I was slightly tickled when I moved here to discover there's an unspoken mutiny in a shop nearby against an incredibly entitled unpleasant woman who does this all the time (seriously she does it 2 or three times a day I've found out since).
She got me a couple of times and I let her go ahead and both times she would then dash off to get something else "quickly" 
Then I saw her a couple of times where someone said No and she did the passive aggressive huffing and puffing rubbish muttering under her breath about people being rude
.
Over time I have noticed that the regulars tend to say No to her. She winges and whines (not quite loud enough to be enough to cause a row).
Eventually I got friendlywith a school mum and we happened to be in the queue at the same time I this shop.
Lady entitled swans up and tries to barrel her way past school mum friend with the airy wave of her hand "I've only got one thing , you don't mind if I pop in front of you?" Already shouldering her way past. School mum friend who is quite bolshy loudly told her No and she needed to go to the back of the queue.
Turns out everyone knows this woman. She does this all the time and is a massive Cf so this wierd unspoken agreement amongst locals came into play. Now none of the regulars will let her pass.
Honestlyjust wait your damn turn. Its so bloody entitled to winge and whine about etiquette when actually you just think your time is more important. It really isn't.