In no particular order.
  1. When Walt throws the pizza on the roof by accident.
  2. When Walt has to get the pizza down off the roof a few days later.
  3. Whenever Walter Jr eats some breakfast.
  4. When Walt throws the mercury fulminate. (obv)
  5. When Tuco yells REALLY loud one minute, but then listens intently to what they have say the next minute.
  6. When Skinny Pete plays the piano that one time.
  7. When Walt doesn't get a milkshake for Hank at Pollos Hermanos.
  8. When we first meet Todd and he seems like a dingus but later on he proves to be a real bastard.
  9. Whenever Walt "uses science".
  10. Whenever Marie gets yelled at by Hank or Walt or Skyler or anyone, really.
  11. When Walt runs over that kid's RC car even though you knew he was going to when you first saw the kid playing with it.
  12. Whenever Jesse stands up to Walt and catches him off guard.
  13. When Gale did karaoke.
  14. When Gale sings in Italian in his apartment and waters his plants.
  15. Towards the end, when Jesse tricks Walt. :o
  16. When Jesse and Walt have obviously aged but they filmed the first "cook" scene anyway and look way, way older IRL.