Remember: just one!
Hands-down, without any question, my favorite 14th episode of SPN is "Plucky Pennywhistle's Magical Menagerie". There's just so much deliciousness going on: the ridiculous deaths, Frank making Dean say stupid phrases to "prove" he's actually Dean, Sam spending most of the episode fighting the urge to scream and run away, Dean trying to help out a young kid and probably emotionally damaging him for the rest of his life ... Good times! :P
That being said, "The Vessel" is a close second, though the tone is completely different--they handle the WW2 stuff with visible respect and care, and it gives what might have otherwise just been a mcguffin hunt some real emotional weight. Not to mention the technical achievement of that submarine interior! (Also, it features some drop-dead gorgeous cinematography.)