The ultimate one-ring, one-pot is a tin of beans and sausages. You can even cook it in the tin which makes it a no-pot.
But with timing, sequencing and the right cheat ingredients you can get quite adventurous.
A fantastic cheat ingredient for camp cooking is Tilda precooked rice. Sachets don't need to be kept chilled, and to serve only need heating through - the packet says microwave or stir fry, but a gentle heat in the pan with a splash of water works just as well. Other great cheat ingredients are the squeezy tubes of herbs and spices, they ought to be chilled after opening but will keep at least a couple of days without if you're careful.
A one-pot one-burner meal from a couple of weeks ago when camping was.. soften chopped onion in oil, stir through squeezy garlic, chilli and ginger; remove from the pan and place in a bowl to one side. Add a splash more oil and gently fry cubed salmon steaks for 3-4 mins, add raw tiger prawns and fry for another 3-4 minutes; remove the fish and place into the bowl with the onions scraping all the tasty bits into the bowl and mixing them through. Add a splash of water to the pan and heat through precooked rice. Serve the rice with the fish/onion over the top. If the pan is big enough you could just pile the onion/fish on top of the rice once it's heated through and give it a stir.
It's a bit fancy for camping with salmon and prawns, but you could do something very similar with onion and bacon, or chicken (or bacon and chicken), or chorizo (or chorizo and chicken - mmm-mmm, making myself hungry here) or any other cured sausage that will cope with ambient (rather than chilled) storage for a day or so. It's just thinking ahead and working out what needs to go into the pan when, and using the resting times to allow things you've taken out to continue to cook through.