So there was this toy back in the 90's and a kid sitting behind us had one and wasn't supposed to, commercial for the things is below. Every time you "slam" the thing down it would start making this stupid laugh that really wasn't all that funny, but in the middle of the pastoral prayer when everything was super quiet and it was only the pastor speaking and praying, the kid sets this thing off (I think it was the blue one at 0.17 secs in the video) and both me and my dad could not help but lose it. It was one of those things where you start laughing and it's contagious and you can't stop. Both he and I had to get up and walk outside to collect ourselves before walking back in!
https://www.youtube.com/watch?v=jDB0oklgLTc