I’ve seen a bunch that are really good, but I’ll add a couple:
BLT. Simple and so so good.
Toastie, or grilled cheese. Couple of ways to punch the is up. Use a thick cut crusty bread. Include some Branson Pickle. I learned about this in London, and it’s amazing. My mom used to make a grilled cheese with tomato and bacon. Either way, or just a plain old grilled cheese is pretty good.