There is always a lot of sharing of brain breaks in the CI community. I began seriously implementing them about two years ago, and man, are they great! Fun, essential, and community-building. If you haven't visited La Maestra Loca's blog to see her amazing collection, do that now. (Well, as soon as your done reading this post!)
One of my students' favorites is a game we call Qui a volé les biscuits de la boîte à biscuits? This is one that can run a little longer than others, but I still love to do it once or twice a month. (It's in the Mafia/Bad Unicorn vein.)

The text of the song in English is 
Class: Who stole the cookies from the cookie jar?
Who stole the cookies from the cookie jar?
Students raise their hands and I choose a someone to name a suspect:
Class: _______ stole the cookies from the cookie jar. (The accused's name fills in the blank.)
________ stole the cookies from the cookie jar.
Student accused: Who, me?
Class: Yes, you!
Student accused says either: Yes, me or Not me!
If the student isn't guilty, the class says, So, who?
We keep playing until the guilty student is found, or I decide we need to stop, in which case students put their hands behind their backs, close their eyes, and I retake the cookie to play again another time (that student will get the cookie a different time). Because I teach younger kids, I have to keep track of who has had the cookie, since everything has to be "fair!"
Let me know if you try this, and what you think!
Bisous.

I have been thinking so much about these ideas since Brattleboro. During her language lab, Annabelle used a fantastic attention grabber: she would cry hola, hola and her students replied with coca cola.  It was extremely effective with both adults and students, and I walked away itching to find something that works as well for me.
With my younger students, I've had a lot of success with a song:
"Mains en l'air, sur la tête, aux épaules et en avant, bras croisés, sur les côtés, moulinets, et l'on se taît."
I'm not sure where I first heard this, but I did find a video that went well with the song, though I only actually show this video to my super littles, as I think the older ones would think it's baby-ish. (Though, it still works wonders with my fourth graders, who learned it as third graders) I also created a poster with some decent images to accompany the song; email me if you'd like a copy, as I'm still figuring out patents and using images and the like.
Anywho, I've been pondering what I could incorporate into my classes, regardless of level. I spent a lot of time talking to folks at the Express Fluency CI conference earlier this month and it started the wheels turning for me. I was striving to find something that would be culturally relevant, linguistically appropriate, and catchy, all at the same time. It made me think of a moment I had a couple of years ago when I was trying to connect with some locals during a summer in France. (Thanks, Tinder!) My friend Romain said during one of our conversations, "T'es sûre que tu n'es pas française?!" ("Are you sure you're not French?!")
I was flattered to think that I had the ability to make a French person say, "Whoa, just how good is this American girl's French?!" So...I thought maybe I could use this to my advantage in my classroom and incorporate some common expressions as attention grabbers for my older kids. I wanted something where the teacher could say the first part, and the students could respond with the second. (In my examples below, the teacher's call is red and student response is blue.)
The two expressions that really caught Romain's eyes were Allons-y/Alonzo, an expression from a Godard film that apparently made its way into Doctor Who! I also love, C'est cool/Raoul. (One could also substitute ma poule for Raoul.) After digging around a bit online, I found some other fun possibilities involving names that have cultural significance.
En voiture/Simone
A l'aise/Blaise
Tranquille/Émile
A la tienne/Etienne
Check out the bottom of this post for a whole list of other possibilities!

Then came the challenge of finding a great phrase for a Brain Break to mirror Annabelle's Chocolate hand game (she explains it, with photos, here on her blog). There aren't many four syllable French words, so I turned to expressions. Here are some possible ideas:
aller-retour
camionette
boîte à conserves
pâtisserie or boulangerie

What other attention grabbers or French-specific Brain Breaks do you have? Please share!
Bisous.

After playing around with the idiomatic expressions with names that I listed above, I moved on to general expressions that I though could transfer to the classroom. Here is what I came up with:
qui plus sait/plus se tait (I like this one because of the meaning behind it!)
mon petit/chou
c'est du/gâteau
crème de la/crême
à toutes/jambes
après la pluie/le beau temps
occupe-toi/de tes oignons
vouloir/c'est pouvoir
laisser les bons temps/rouler
​chose promise/chose due
le temps/c'est de l'argent
pas de nouvelle/bonnes nouvelle
petit à petit/l'oiseau fait son nid
quand le chat n'est pas là/les souris dansent
qui va à la chasse/perd sa place
plus on est de fous/plus on rit
qui se ressemble/s'assemble
tel père/tel fils
on est tous/dans le même bain
un sou/est un sou
l'erreur/est humaine (or, divided differently, l'erreur est/humaine)
l'union fait/la force (or, divided differently, l'union/fait la force)
quelle/salade (I'm not sure how I feel about this one, I think the fact that the teacher's call is only one syllable could be challenging.)

These expressions could also be used as passwords à la Bryce Hedstrom, and incorporated into class in a plethora of ways.