We last updated this answer in November 2016. Though some of these casinos have had their coin slots forever, others come and (mostly) go. The old coin-accepting slot machines are slowly disappearing, but can still be found at the following select casinos.
Slots A Fun has 10 coin-in games left and Circus Circus has approximately 40.
All three Boyd Gaming casinos in downtown Las Vegas -- California, Fremont, and Main Street Station -- still have coin-operated video poker, along with a pair of Blazing 7s machines at the California.
Also, Boyd recently bought Eastside Cannery, which has a salon of coin-in machines.
However, Boyd spokesman David Strow says, "As we haven't completed the acquisition of Eastside Cannery yet, [it is] too early to speculate on what we might do there."
The El Cortez, we were told, has "probably a hundred" coin-operated machines.
Downtown, the Plaza Hotel has "roughly a half-dozen" coin-in coin-out machines.
And at The D, owner Derek Stevens continues to maintain a vintage-slots area upstairs, including one of only two Sigma Derby machines in Nevada. We think he deserves extra props for that.
In Jean, Terrible's Road House (formerly the Gold Strike) had coin-in slots when still owned by MGM Resorts International, but new owner Jett Gaming has switched to ticket-in ticket-out (TITO) machines, which dispense the paper-redemption coupon instead of coins.