AlmaArmas_ said:
Bologna with BBQ sauce is an underrated combo.
Hmmm...
I can't see bologna going well with the tangy, tomato-based BBQ sauces that are the norm here, but there are many other varieties of BBQ sauce that are popular elsewhere. I can see bologna going well with the mustard-based BBQ sauces from the Carolinas.
Back to the question at hand, it comes down to either roast beef or smoked turkey as my favorite sandwich meat though I do like most of the others as well. Leftover sliced meatloaf is great for making sandwiches too, but I don't think it officially counts as a "sandwich meat".