@Susan4269 Things like coffee, tea, and the fixings for those, cooking oil, spices, salt and pepper, individually packaged snacks like granola bars, etc, are fine to leave. It's nice to top the containers up between guests, so they get the impression it's fresh for them.
Partial containers of mayo, mustard, jam, butter, etc, are generally a turn-off for guests and make it seem like you didn't bother to clean out the fridge between guests.
No one knows whether the last guests stuck a knife in there they had licked off, or whether it had been left out on the counter unrefrigerated for hours - it's a health hazard as well as aesthetically displeasing.
I know it's quite upsetting to many of us to have to toss what seems like perfectly good food, so either use it yourself, or donate to a local homeless camp or shelter or some poor college student you might know. Young men will eat almost anything 🙂