I'm very partial to the W124 and the R129. I wouldn't trade my 91 300D for any other car. Well, maybe a 500E.
1976 300D (W115) - 330K and still going (sort of)
1991 300D 2.5 Turbo - Sold at 221K
1983 280SEL - Sold at 206K
1981 300SD - Sold at 232K