Severed toe.
Just kidding. It was a penis.
A somewhat larger vial of Motown record producer Barry Gordy’s blood.
A human foot.
Turned out to be a candy human foot–it was Halloweentime, after all–but it was quite the shocker. Protip: don’t eat the bones. They’re edible and are supposedly candy, too, but they taste more like ass than foot.
I left a wide-eyed trout in my mom’s freezer when I went away to college. She never mentioned it, but it was gone when I came home for the holidays.
A plastic bag with six or seven sheep’s heads, skinned, but otherwise complete. Rhiannon8404 knew someone who had a sheep farm; they raised them for wool, but would eventually butcher the sheep when they could no longer produce, and sell the meat. We bought it primarily for dog food, and since most people didn’t want the heads, we would get a bunch of them thrown in for free. The dogs love them.
I’m assuming this was a large chest freezer?
“I’m keeping it for a friend, really!” 
Not my house, but at the grocery store pharmacy. One Sunday, I decided to defrost our dorm-sized fridge where we stored our insulin and other cold-storage meds, so I brought in a cooler, some towels, and my hair dryer and unplugged the fridge because the freezer had condensation so thick, we couldn’t store anything in the freezer.
So anyway, as the ice melted and I peeled chunks of it off the metal surface, I found several foil-wrapped chocolate Easter candies of unknown vintage, and several other things I couldn’t identify and therefore discarded.
p.s. Were (are?) Otter Pops in clear plastic, and melted rapidly? If they were, my grandmother always had those on hand. They were colored sugar water, and so messy.
When I was in college, I lived in an un-air-conditioned apartment and sometimes put my clothes in the freezer before getting dressed, just to have a few minutes’ respite from the heat.
…which reminded me of the old slumber party prank of soaking a bra in water and freezing it if a girl fell asleep.
I don’t think this of this as strange: paint brushes.
When I’m painting with water based materials I wrap up the still loaded brush(es) with plastic wrap and stick them in the freezer until the next day. No need to clean them. I’ve never noticed a smell or flavor contamination. Remember to take them out before use to thaw. It’s my understanding that this is a common painters trick. As Fred Dryer used to say “Works for me.”
P.S. When I finish the paint job the brushes finally get cleaned and stored in their proper place.
May I direct you to the menopause thread?
https://boards.straightdope.com/sdmb/showthread.php?t=836549
Small boxes of baking soda. So weird. Every time I find one in there I put it back in the cupboard where it belongs. You can’t bake with frozen baking soda.