All time favorite. Majora's Mask, hands down. No other Zelda title comes close.
Least: well, lets just say, I didn't even finish phantom hourglass. Just an awful, awful one.
And I may commit Zelda blasphemy by saying this, but I didnt really care much for skyward sword. It was an amazing story, fantastic dungeons, bosses, puzzles, and graphics. And ghirahim... i just loved him. So why did I not like it? Too much emphasis on motion controls, too much back tracking, and busy work. Once i beat it, i never picked it back up again