As well as Cowboys and Indians, we also played marbles a lot as kids. We played at home and we played at school even though the teachers always threatened to take the marbles away - something about them being dangerous.
Anyway, back in Primary school (P4 - which made me about 9), we were all settling back into class after lunch. Apart from one boy - I think his name was Peter - who was busy playing with his marbles. He kept throwing one in the air and catching it in his mouth before spitting it back out. He was doing this behind the teacher's back as she addressed the other side of the class. We were all trying not to laugh and would have succeeded if he hadn't thrown one marble in the air, caught it in his mouth and promptly swallowed it. He gave out a gargling yell before the marble stuck for moment and he leapt to his feet going "ack, ack, ack" and pointing at his throat. We all thought he was having us on. Luckily the marble came loose and went all the way down. The teacher turned to ask what was wrong and between sobs Peter told her he had just swallowed his favourite marble.
She ushered him out of the class and a doctor was sent for. Peter was taken to the hospital and told the marble had gone all the way into his stomach and should work its way out naturally. He took great delight in telling us the next day that he and his mum had to search through his s**t until the marble was found.
Funnily enough, everyone else was kind of reluctant to play marbles with him after that.