JET 26x80 Geared Head Engine Lathe (6,700lb)
The heaviest object we could find that ships free on Amazon is this three ton powered lathe. Weighing significantly more than a car, and requiring special delivery agreements — no one-click ordering available — you'll have to be home when it's delivered. But with something this large you'll probably want to be around when it arrives.
NVA Creative Garden Granite Wilma Bench (319lb)
If your home's decor would benefit from a giant slab of granite, you're in luck. You don't have to worry about freight costs when it comes to this rustic and durable bench. But you might have a few other headaches, as the listing notes that "minimal assembly" is required.
CAP Barbell 300-Pound Olympic Set (300lb)
Only Prime-eligible in certain colors, this weight set will give you the ability to work out at home, unfortunately you won't be able to pump up before having to carry them into your house.
SHOP FOX W1756 25 HP 43-Inch Three Phase Wide-belt Sander (2,537lb)
Just think of all the great things you'll be able to do with this $16,000, variable-speed sander. And it may be one of the best deals you can find: Not only is Amazon selling the machine at a $4,000 discount, but there's no shipping to pay for this 2,500-pound beast.
Genuine GM 19201332 Assembled Kit with Aluminum Head (674lb)
This engine only works with one car, but it's one of dozens available through Amazon's auto section. Most are Prime-eligible, or otherwise ship free.
Stack-On TD14-22-SB-E-S Fire Resistant Waterproof Fully Convertible Total Defense Safe with Electronic Lock (463lb)
Originally thought to be the heaviest object to ship for free through Amazon Prime, a gun safe, or safe in general is bound to weigh a ton, or in this case a quarter of a ton. A word of warning, one review mentioned that the delivery people refused to carry this up to the buyers apartment, making the shipping free but the delivery a costly expense.
Nissan Versa Note (2,414 to 2,523lb)
Ok. This only happened once, but Amazon and Nissan did partner up for a promotion that let people buy its cars online. One lucky winner would have the car delivered in true Amazon-shipped fashion, in a larger-than-an-NYC-apartment box. Reddit user "listrophy" snapped a photo while the car was in-transit, and the image spread around the internet. Despite the surprise being blown, Amazon still made a commercial about the ordeal.
