Things jangling when cycling or running, especially on others!
I need both a fob and a key to get into my house so have bound them with a rubber band to keep them quiet when they are in a pocket or top tube bag.
I ran the London Marathon one year and there was a chap in full Morris Dancer kit running at the same pace. With every stride the bells around his knees would jingle jangle. I stuck it for a mile or two then just had to up my pace to get away from him.