I read somewhere (almost certainly apocryphal) that peanut butter was originally conceived in Jamaica as a spread for toast, so I gave it a go and have enjoyed it like that ever since.
Very little beats decent thick toast with loads of real butter melted into it, perhaps with a touch of salt sprinkled on top.
Beyond that, I don't know if I can choose just one favourite thing. Cheese & tomato with basil grilled up (pizza, essentially), various pates and terrines, Vegemite™ (not Marmite™, if I can help it), pineapple cottage cheese, bacon and/or ham, Spam™, scrambled or fried egg...
One that you kinda have to try is SOS - **** On a Shingle.
Recipes online. Basically chipped beef in a creamy, mushroomy sauce on toast. It's an old WW2 army recipe, but surprisingly good. Far better than those Toast Toppers™ and hard to imagine ******* it up SO bad that it earns such a derogatory nickname.
