1990 BMW 5 Series 525i 4dr Sedan
This car has served me very well in the past 3 years. I used to commute 100 miles every day and it didn't miss a beat. I put in a rebuilt head, which it didn't really need, but other than that I have 50K on it since I bought it and it hasn't taken any money to maintain since the cylinder head rebuild which cost me 3K. Other things to go bad are the thrust arms, remedied by installing urethane busings at a cost of $200.
Straight 6 engine is awesome in city driving, great handling, comfortable.
It really needs 40 more horsepower but in that case you can get the v8 540i. Couldn't affort it and maintenence is way more expensive so I live without 250 HP.