(Mine are all food related. And these are just MY versions of what I feel are "white trash", yours may vary so if I offended you with my choices, good!! :P )
Cool Whip. No way I'd buy that stuff now, but my mom bought it and put it on everything desserty. Jell-o, pudding, pie, you name it.
Braunschweiger. Poor mans pate. Another sandwich staple in our household. To this day I crave it once MAYBE twice a year.
Creamed tuna on toast. A Lenten Friday night delicacy. It was the Catholic version of chipped beef on toast.
Miracle Whip. Again we were raised on this instead of mayonnaise. Nowadays there's only one thing I can stomach Miracle Whip on, turkey sandwiches (on white bread) made with Thanksgiving leftovers.
Margarine (or as my parents called it, oleo). Not sure why they bought this instead of butter, maybe it was cheaper 30-40 years ago???
Cragmont or Shasta soda. No Coke or Pepsi for us, it was this stuff.
Getting McDonalds on a Saturday night to bring home, and not being allowed to get a drink. "We have drinks at home, you don't need one from McDonalds".