The most delicious crab apple I've sampled, from anywhere in the
world, is called 'Kerr'. It tastes like a Gewurtztraminer wine - or
somewhere between champagne and a Moscato... incredible. Last I
checked, It was kept at the USDA Germplasm repository at Geneva, and
therefore is probably available for distribution. Another fascinating
crab is called 'Novosibersky Sweet', which is uber-sweet and has no
tartness at all.