"Three Stories". Especially this piece of heartbreaking conversation in one of the flashbacks:
Stacy: We've got to let him cut the leg off.
House: (in massive amounts of pain) It's my leg. It's my life.
Stacy: Would you give up your leg to save my life?
House: Of course I would.
Stacy: Then why do you think your life is worth less than mine? If this were any other patient, what would you tell them to do?
House: I would say it's their choice.
Stacy: What? Not a chance! You'd browbeat them until they made the choice you knew was right. You'd shove it in their face that it's just a damn leg! You don't think you deserve to live? You don't think you deserve to be happy? Not let them cut off your leg? (They're both near tears.)
House: I can't, I can't, I'm sorry.