Game time fatty.
What to put inside?
pickled jalapeno, grilled onion, grilled mushroom & BBQ sauce!
i guess when it comes right down to it, there are only really a few things a guy can put on a burger!
Lots of cheese. The bacon on the outside and the cheese on the inside. Chopped peppers of any kind. If fresh, they should be sauteed a little first. More bacon. Fry up some, chop it and put it inside the fatty too. Hard boiled eggs, chopped black olives. Maybe a bit of cilantro, chili and cumin powder. And as kinyo said, onion. I could keep going.
Franks hot sauce and blue cheese
Caramelized vidalia onions, ketchup and Tabasco sauce (or Heinz Ketchup flavored with Tabasco). The black olives sound good.
Sautéed onions and mushrooms along with bacon bits, cheddar cheese and BBQ sauce!
GAME TIME fatty?
Well heck, nothing beats a great smoked chili - with plenty of sauted onions, sprinkled with smoked cheese - a harsher tasting cheese is best!
Also, naturally produces the great game time humour of "OK, who cut the smoked cheese""