Homemade compound butters in rolls/slices. It's easy to grab to top a pizza (homemade cheesy garlic bread 😍) or steak.
I buy whole, peeled garlic cloves and then freeze them whole. Or chop a load in the processor and freeze in giant ice cube trays (garlic is measured with the heart).
Lemon slices for drinks.
Chicken carcasses and veg peelings for stock (and the resulting, heavily reduced stock).
Fresh herbs, ginger and chillies (to be grated from frozen).
I make up double batches of curry sauce (mowglis butter chicken is a firm favourite here) and freeze half for an easy dinner.
Parmesan rinds for umami/cheese puffs 🤌🏻
I freeze double cream in 2 tbsp ice cube trays for adding to sauces.
Egg yolks/whites/whole eggs that have been whisked up. If I have eggs that are coming up to their date, I'll often freeze them, whisked up, ready for Yorkshire puddings/pancakes.
I make up stuffing mix and freeze in portions, that can then be cooked from frozen.
Same with cauliflower cheese. I freeze in individual florets and then add to a bag. Then i can just pull out as many florets as i want and, again, cook from frozen.
I freeze the ends of loafs for stuffing/meatballs.
Cookie dough so I can just cook as many as I want at a time.
Butter. I like president spreadable, so I buy when on offer and keep it in the freezer.
Milk also (although thanks to whomever said about freezing it in ice cube trays!).
Also, I feel like this is a group who would appreciate a souper cube. They're basically giant, silicone ice cube trays.