The W110 fintail (Heckflosse in German) generation of Mercedes-Benz executive class sedans was built in 2 series from 1961 through 1968. Today, the W110 won't be on the podium at any drag races, but it offers a leisurely approach to vintage car ownership. Find this 1966 Mercedes-Benz 230 here on eBay bidding for $2,801 with 2 days to go, located in Fort Wayne, IN. 
The Mercedes W123 series was the predecessor to the modern E-class
sedan and is known as one of the most rugged cars ever built with
examples running millions of miles all around the world. A W123 won't win any competitions involving speed or handling, but
if you ever need a car to play tortoise to all the other hares, this is
it. Expect the engine to outlast just about everything else on the
road and the chassis will take an amazing amount of abuse and just keep
on ticking. Find this 1981 Mercedes-Benz 230TE W123 offered for $6,000 in San Marcos, CA via craigslist.
The Mercedes-Benz W110 is a classic sedan from the
mid sixties and has gained the nickname Heckflosse (German for
Fintail). Technically, the rear fins were called peilstege (German for
sightlines) and weren't designed for aerodynamic stability, but to help
the driver find the ends of the car when backing up. A decent running/driving example with nice paint for less than $4k seems almost too good to be true. You be the judge. Find this 1967 Mercedes Benz 230 offered here on craigslist for $3300 located in Fresno, CA. Tip from FuelTruck.
This 1967 Mercedes-Benz 230 W110 Heckflosse (Fintail) is currently for sale in Ashburn, VA for $3,450 with a few hours to go. The car is currently offered on a no-reserve auction and is going to cheap, but it has recently had a respray that the seller admits has some flaws...and everybody knows those sort of flaws only get worse as paint job ages in the first few months. Still, its a lot of vintage metal for the money.
The Mercedes-Benz W111 was the equivalent of an S-Class Mercedes in the mid sixties and has gained the nickname Heckflosse (German for Fintail). Technically the rear fins were called peilstege (German for sightlines) and weren't designed for aerodynamic stability, but to help the driver find the ends of the car when backing up. We would welcome such appendages in most modern sedans whose monstrously high belt lines (for "style") have turned locating the bumper into a game of bumper tag. Ironic that a modern S-Class lacks both the style and function of a classic W111. This 1966 Mercedes-Benz W111 Heckflosse is for sale in frosty Anchorage, AK via craiglist for the hot price of $5,500. Thanks for the tip from ANCMatt. 
We at the DT love classic 60s/70s/80s Mercedes cars for good looks, rock solid build quality (before the marketing weenies in the unholy Daimler-Chrysler years took over and forced engineering to compromise quality in an exchange for wild dreams of market share) and they are rarely seen in the wild. The 4 door W110 sedans are a bargain today and we originally we had our eye on a 67 MBZ 200 on ebay (bidding at $1425 reserved not met)- but then we found this 1966 Mercedes-Benz 230 Hechflosse on craigslist for $3950 located in SF Bay Area, CA.