2005 Ford Focus ZX3 S 2dr Hatchback (2.0L 4cyl 5M)
I plan on keeping this car for the next 50 years! I've had no problems with it at all, and the gas mileage is fantastic on the freeway. The EPA estimate is 35 HWY for my model, and on my last trip I got 34.8, while going 70 or more with no AC. No mechanical problems at all, and it's compact size is great for maneuvering in Los Angeles. The car costs nothing to operate besides the $19.99 oil change I get religiously, and gas.
Gas mileage, reliability, price.
It's a bit noisy inside, and my plastic wheelcovers squeak. City driving gas mileage is less than EPAs estimate of 27. It probably gets in the low 20s, but this is in LA traffic.