Some folks have tossed around the Saturn idea...the SOHC is a great choice if all you're after is MPG, but...well, let's just say that at 85k my brother's '96 Saturn was TOAST.

Another vote for a civic here - I know mine (an 04 auto) can pull 30 mpg in city without trying, 40 if I take backroads...and I'm sure the older ones which are lighter can pull higher numbers.

Although...a convertable for pizza delivery is an interesting idea, as you might as well have fun driving around all day...:p