Walmart offers the refurbished Apple iMac Intel Haswell Core i5 Quad 2.7GHz 21.5 Desktop, model no. ME086LL/A, for $799 with free shipping. That's $50 under our mention of a refurb from three weeks ago and the lowest total price we've seen. (It's also $100 less than you'd pay for a new one.) It features an Intel Haswell Core i5 2.7GHz quad-core processor, 21.5" 1920x1080 (1080p) LED-backlit IPS display, 8GB RAM, 1TB hard drive, Intel Iris Pro Graphics, 802.11ac wireless, Gigabit Ethernet, Bluetooth 4.0, Magic Keyboard and Mouse, Thunderbolt, USB 3.0, and Mac OS X.
A 90-day warranty applies, but it's unclear who backs it.