You have been waiting in line for ten minutes. Someone cuts the line in front of you.

Vous faites la queue depuis dix minutes. Quelqu'un passe juste devant vous dans la file d'attente.

ask that someone to go back to the end of the line
Ask them to get into the back of the line, like everyone else.
Depends on how patient I am feeling and if I'm in a hurry and if I've been having a delightful conversation with the other people in line... or not. If I'm annoyed, I will point out to them, loudly enough so that everyone else they cut in front of can hear, that the end of the line is way back there.
I glare at them.
I say, "excuse me, the line starts there"
I tell him that there is a line and should move to the back
I would be angry at the person but I wouldn't say anything to them.
I would perhaps look hard at the person, but not do much of anything else.
I would politely tell them that they cut ahead of me and ask them to go to the end of the line.
I would say 'Excuse me,' and depending on his (her) reaction, I would either ask that they move or pay no attention.
I would say something to them about not cutting in line.
If he doesn't have a friend on the line, I attack him verbally.
ignore or ask them to go back if annoyed
It depends on how big of a rush I'm in.
Kindly tell him that there is a line.
Not a big deal.
Tell them that there is a line and ask them to move
yell at them for being disrespectful

honnêtement, qui ne l'a jamais fait?
je dis "bonjour vous avez perdu quelque chose ?"
je fais un commentaire ironique à voix haute et je lui laisse la place.
je l intercepte et je lui fait remarquer que des personnes font la queue et qu il peut la faire comme tout le monde
je la laisse :"Tant pis !"
Je laisse passer et je dis "merci !".
je le double à mon tour
Je le regarde froidement et repasse devant lui. S'il recommence, je lui explique le but d'une file d'attente et le remet en place.
je lui demande poliment de passer derrière moi car j'était là en premier
je lui demande pour le principe de faire la queue comme tout le monde
je lui demande se qu'il veux,et si il est comme moi je lui dit que la queue et là bas. Il y a d'autre gens qui son ds le meme cas que vous.
je lui dit d'aller derrière et de faire la queue comme tout le monde
je ne supporte pas et correctement je lui fait une remarque
je rale
je repasse devant lui, avec un air très énervé.

Discussion

doing nothing

In this situation, several responses on the American side seem to involve annoyace at the person but unwillingness to confront them. I think a reason for this is that Americans tend to avoid confrontation, and no one can be sure how the person will react if you criticize them. This discrepancy in the willingness to confront someone appears in a few other situations too. Are people always so direct in France, or are there people who would react the same way these Americans would?

cutting them back

Several French students wrote that they would step in front of the person who stepped in front of them. Is that to make a game out of it, or is that a serious way to tell them that it annoys you?