Well, nice is in the eye of the beholder.....you could go classic like my silver 1980 300sd (super diesel, w116 chassis):

Or something more modern, like this one, similar to my black 1982 300SD (super diesel):

It's bigger brother, the 300SDL (super long diesel):

Maybe smaller, a later 80's 300d (w124):

Or the compact, a 1988 190D:

Or maybe one of these, a 300CD (coupe diesel) a sporty coupe sedan (and rare as hen's teeth - I'll send you an email of someone who was selling one for around $5800 or so).

Any classifications you look at starting with a "w" (i.e. w126) is a chassis style, with different models built on that chassis ( like Cherokee and Comanche on the same chassis).
Easy and simple vehicles to work on,
www.mercedesshop.com has tonnes of guys there who can tell you anything you need to know, and they're very reliable. Great mileage, nothing like a new Jetta, but no slouches either. Gassers are pigs, though.