There seemed to be a thing a few years ago when loads of people were banging on about asking for one when you check in, and about how likely you are to get it, because the airlines have loads of free seats in first class and don't really lose out from swapping you over. I've never done it, though I've wondered about it. My parents managed it on a short-haul trip when he mentioned to them at the desk that it was their anniversary.
Have you ever got one? Any other freebies, just by being a bit ballsy? Don't ask don't get and all that.