Which human foods can cats eat? Not as exclusive diet, but once in a
while, without harming their health.

Its not "human" that matters. Its natural and non-processed. Look at your
cat food's ingredients. They make it so it won't spoil in non-refrigerated
conditions. Do you know of any food besides perhaps nuts and sees that
stays pristine in non-refrigerated conditions for very long? Also - no
animals should ever eat cooked foods. Have you ever seen a stove in a
forest? Its a natural thing for animals to be fast and lean to catch their
foods. So fat animals will naturally lose their excess weight in the wilds.
Its absurd for domestic animals to be heavy. Of course its absurd for
people to be heavy...but that's another story on modern society's rapidly
declining health.

A casual glance at our fridge shows: cooked shrimp, baked chicken, ham,
bacon, sausage, canned tuna, salmon. Oh, and I just scambled some eggs
for myself.

Ham, bacon, sausage - the worst meats one could possible ingest. Filled
enough with enough preservatives to kill ya - slowly!

All of this is non-vegetable. Can cats eat it safely?

BTW, what makes canned cat food stink so badly? :-)

Not enough preservatives maybe?

Real food for cats? Raw, fresh fish and meat. And whatever small amounts
of greens/vegetables they might supplement that with. Liver is very cheap.
I'm no cat expert; just trying to use some logic.