M&S used to do a Bacon and Avocado sandwich which was delicious. My favourite home made sandwich has to be the good old cheese and onion - grated strong cheddar and slices of raw onion. Mind you, you can't talk to anyone for the rest of the day, but it's a small price to pay
White bread, whatever meat I have at hand (usually turkey, pepperoni, salami and/or ham), whatever cheese I have at hand (some combination of sharp cheddar, swiss, pepper jack, american and feta), and as much A1 steak sauce as the sandwich can hold.
If I'm feeling lazy, I skip the bread and meat, and just pour steak sauce on slices of cheese...
Many versions exist under the same name, but the one I am familiar with is fried bread with an egg in the middle. You cut a hole in the middle of a slice of bread with a wine glass or something, then slap it in a frying pan with hot oil and crack an egg in the middle. Cook for a couple of minutes then flip it and do the other side. If you want a runny egg you just crack the egg in after it's been flipped. You fry the circle of bread you cut out too (can't be wasting food) and it can be a little hat for your egg.
PS. I think most people just call a fried egg sarnie an egg banjo sarnie.
"You're a big man, but you're in bad shape. With me, it's a full time job." – Lt. Bromhead to Prince Dabulamanzi before the Battle of Rorke's Drift.