My favorite kit so far has been Midwest's Liberty Cream Ale with Wyeast Am. Ale# 1056, a very basic kit with steeping grains but at 6 weeks in the bottle this beer has been the most requested re-brew I've done so far
Brewer's Best Irish Red. SWMBO LOVES this beer so much, I took the recipe and converted it to all-grain and brew 10 gallons at a time. And only after 50+ gallons started shifting the recipe slightly just to change it up a tiny bit.
A great man knows that he knows NOTHING