Whistles. More than one every once in a while gets tiresome :/. I also despise absurd map layouts that have you going back and forth over just two or three notes for the sake of it. And never forget a bunch of notes 'streamed' so far apart that you can actually miss them all not only because you're going to fast, but also because they're so far apart you try to press far before you're on them. Whistles though, get a second mention. I don't mind claps or any other random sound (for real, tennis balls and doors) but whistles blow your focus, particularly when abused. T-T.