I try to keep the following in my fridge at all times.
Milk, Crystal Light (pitcher)
Deli meat, bacon, eggs
Cheese: shredded marble cheddar, some deli sliced cheese
Veggies: Onion, lettuce, tomato ... basic stuff for sandwiches
Sauces: Mustard, Spicy Mustard, Mayo, Soy Sauce, BBQ Sauce, Siracha, Worchestershire,
Butter (salted)
I don't keep a lot on hand in the fridge. Most things that I would put in the fridge I'll buy the day I make them.
Edit to add hot sauce: Louisiana, and some sort of chipotle hot sauce (currently cholula)