Mine was first season near the start. "Solitary."
It's the one where Sayid leaves the beach because he tortured Sawyer. I love Hurley building the golf course. Some great lines there with the Rashy guy. "Are you playing golf!? Can I play?" We get to find out Sayid's back story We get or first clue that there are other people on the island. Sayid hears the whispers. Loved it.

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Hope is a very dangerous thing to lose. - Sayid

I do what my Rice Krispies tell me to. - Anonymous