In the past, I've sworn by Brandywines, but they're a warm-season variety not really suited to zone 4. Each year I'd lose many more to frost than would ripen. This year, I grew a hybrid called Celebrity, and have been pleased as punch with it! The plants started well indoors under grow lights, and really took off when moved to the greenhouse then garden. The fruits are medium-sized, virtually blemish-free, and have a great flavor! I will definitely be growing these again. Among the small tomatoes, I really like Yellow Pear. Very low in acidic ... great to snack on right off the vine, and makes a pretty salsa, too! What are your favorites?!