Of all of the kits that I have built, I still like Bruce Tharps Delta Vortex (built 2), and Northeast Aerodynamics Twinair.
Bruce's kits, as mentioned by other posters have excellent parts fit, quality wood, and well thought out assembly instructions. On top of all of that, you end up with one great flying plane. Can't ask for much more than that.
The Northeast Aerodynamics Twin Air, is another kit with very good parts fit, and quality balsa. This kit is a good one to modify into something totally different looking than the original. I haven't quite finished this one, but the flying reports are good for the Twinair. I am also partial to the Ultra Sport looks, and have modified the Twinair to resemble an Ultra Sport with twin engines. The only problem I have with kit building, is that some of my projects get shelved for periods of time, and take a wile to get finished.

Here are pics.