All of the above plus
Dodgy mouse (though possibly also a case of greed). Had a cat that would eat a mouse, come in, eat biscuits from his bowl, throw the lot up into the bowl, take a step sideways to the other bowl with the fresh biscuits (we had two cats) and start eating again. He didn't fancy the soup of lightly diced mouse bits (recognisable bits), stomach juices, blood, with cat biscuit croutons. The fresh biscuits would stay down.
Cat biscuits. Had an old cat from the rescue centre with really bad teeth. The vet said to make him eat biscuits for the good of his remaining teeth (to clean them). If we put cat biscuits down he'd nibble at them in a pathetic way, then throw them up ten minutes later. If we put down high quality tinned food he'd ignore it. If we put down the most disgusting, humming, cheap tinned cat food he'd lick the bowl round the floor getting the last little bit and keep the lot down.
Spiders. They seem to be chucked up half the time.