Un coup de gueule  =

Expression de mécontentement  / protestation

Having a rant / a fit/ a strong protest

Marc, maybe you are talking about a horsefly?  = taon in french (that's the only nasty fly we have here)

I love your Canadian idioms!

another one:

Mise en boite: leg pulling, ridiculing someone   /   railler, se moquer de quelqu'un

Lit: placed / put in a box

Haha You're lucky here in the north and in forested regions we have flies that bite. They are quite annoying and never quit until you kill them or they bite you. Contrary to mosquitoes they literally rip off a part of flesh. So it's painful and their persitance may drive you mad. I hate camping because of that. So this expression could be litteral.

They are called Mouches noires (funny since they differ from regular flies by having white spots) or the meaner variety Mouches à Chevreuil (although they may not really be in the fly family they are almost as big as a bee).

But since it's an idioms discusion here we go.

J'ai mon voyage! (I'm (really) fed up) lit: I have my travel (does not translate well) Not sure of the origin but it's used frequently here.

Se faire passer un sapin (to be lied to) lit: to have someone pass a fir tree through you.

Or one of the weirdest but still used frequently

Habillé comme la chienne à Jacques : (Being badly dressed) lit: Being dressed like Jacque's female dog.

The legend is that some guy named Jacques had a sick female dog that lost it's hairs so since it's really cold in the winter he would dress it with old unused clothes and coats. So people would compare badly dressed people to that dog.

Quelle mouche l'a picqué? : What's the matter with him / what is he doing?  

                                       Qu'est-ce qui lui prend, qu'est-ce qui lui arrive?

Lit: which fly stung him?  (that is quite funny because flies don't sting?) 

Here is another one:

avoir un chat dans la gorge :  to have a frog in your throat   /   avoir la voix enrouée

(lit: to have a cat in your throat)