Ending today, Newegg offers the refurbished Asus Dual-Band 802.11ac Wireless AC1200 Gigabit Ethernet Router for $39.99 with free shipping. That's tied with our mention from a month ago (although that required a mail-in rebate) as the lowest price we've seen. (It's the best deal for a refurb today by $20 and $45 less than you'd pay for a new unit.) It features 802.11ac wireless, data transfer rates up to 1.17GB/s, four Gigabit Ethernet ports, and USB 3.0 for sharing printers and hard drives.
Note: A 90-day warranty applies, although it's unclear who backs it.