Initials for the band My Chemical Romance. Used mostly on the internet, but there are those douchebags out there who use it in everyday speak.
Me: *hums Headfirst for Halos silently to myself*
My douchebag friend: ARE YOU SINGING MCR?
Me: No, I wrote it.
My douchebag friend: Oh... it's kind of cool.
Me: Yes it's MY CHEMICAL ROMANCE.
My douchebag friend: I KNEW IT SUCKED!
I swear, it was more or less like this when it happened. Kind of sucks, but whatever floats your boat.