Husband kills wife because she burnt a hole in his favourite shirt when she was ironing it. The weapon was the iron.
Japanese mother kills neighbour’s toddler to secure last place at local nursery for her own child.
Driver of ice-cream van murders rival with a home-made sword after a clash for the best spot for selling ice-creams.
Man kills wife and four others because his breakfast eggs were cold.
Chinese computer-gamer murders his friend for stealing his dragon sabre – a virtual object in an online game.
Lawyer (yes, a lawyer!) kills person sitting next to him in a cinema after an argument about noisy eating of popcorn.
Probably not a good idea to use any of these in a crime story. Your readers wouldn’t believe them. Do you know any other (genuine) weird ones?
Malcolm Rose is the bestselling author of the Jordan Stryker and Luke Harding series, among many others. When he says they aren't his own mad motives, I think he's another one who's protesting too much (see Anne Rooney). Re the popcorn, I'd have done the same as the lawyer.