Not so much a chant or a sign but once I went to a protest of the war in Afghanistan. First there was a planning meeting. The people “organizing” this protest knew absolutely zero about how to get anything done.
Eventually I nominated myself to write a few bullet points on the board, then ask people who was gonna be in charge of what thing.
They were blown away. Asking how I knew how to do that.
Then later, we had the actual march. Our column was completely surrounded by police the entire time. Like we were a big rectangle going through the streets of Chicago, and the outer layer of that rectangle was a solid wall of officers.
I got to heckle the Westboro Baptist Church who were protesting at Obama's first inauguration. They made the mistake of impeding VIP traffic and the Capitol Police rounded them all up. Good times.
I won't repeat their chants here, though, given the content.
"ALCA não! Álcool sim!" (no to FTAA! yes to alcohol!)
Okay I'm being slightly unfair because the "chant" in question was mostly a joke among the members of a bunch of small political parties, but it was seriously a damn shitty joke.