I'm going to side on what the OP might be happy with because if he/she isn't happy with it they aren't going to keep it, and some improvement beats no improvement.
I think you will be happy with just about any mid-full size sedans v6 or smaller. They should get you into the range of mid 20's to low 30's.
If your wanting more of a truck most of the midsized ones (Frontier, Tacoma, Ranger, Colorado...etc) should get you into the mid 20's as long as you don't go crazy with the optons.
Some of the midsized crossovers can even get you into the high 20's.
Just take a look and see whay the EPA ratings are to give you at least an Idea what you could start with.
Fuel Economy