There's one group of Christians who are really obnoxious and they frequent professional sporting events in the US. Their signs are typically yellow I think, with messages to repent and to go to church, etc. Usually have a loudspeaker as well. I've seen them in LA, Seattle, Phoenix and some other places.
I mock them.
I asked a teenage kid once on the loud speaker outside of Angel Stadium if its a sin to watch a baseball game and if I should be going to church instead at 7:00PM on a Tuesday. Blank stare.
EDIT: Haha I found them