While playing a show in Europe, some guy (who was obviously a jerk) threw a coin at the singer of Bloc Party two songs into the set. They took a quick break and got right back on. Well done, they could have been jerks about it and they weren't. Kudos.
People who were not cool with fans throwing stuff:
Panic At The Disco singer gets knocked out with bottle:
Nickelback singer/resident horse gets hit with rocks.