One of my own favorites, which might vie for #4 or 5 is from season 6-- Lessons.
Maybe it's because I'm a musician and realize the bonds that can form between players, but it's well done. As for the part where Nella and her crew are trapped on the planet and nearly are incinerated, well, I guess there has to be some sort of adventure. With Picard playing his Ressican flute, it's a flashback to The Inner Light. Oh, and let's not forget the roll-up piano!
Another, for its psychological impact, is Frame of Mind. There were points in the episode even I wasn't sure which was real and which was the fantasy. Similar in that respect to Total Recall.
Really, it's like being a kid in a candy store to pick just a few favorites-- I even sometimes enjoy the ones that showed up as the bottom 5.
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