There are three different scenes in Hug that I love.
The first is the loft scene between Clark and Lana, where we see something that would be all but impossible to imagine in later seasons. Lana is pissy because Clark has had the audacity to disagree with her, and Clark delivers a full-on Lana smackdown! He's angry, he's dismissive, he doesn't apologize, and he doesn't give an inch on his position. I never get tired of watching it!
The second is when Lex, under the influence of Rickman's touch, goes after Clark and Kyle at the gas station. It's the first glimpse we get in the series of the torment Lex carries just beneath the surface, how he feels about being so different, and how much Clark's secrecy wounds him. Michael gives an amazing performance, especially in the way he portrays Lex's chilling ruthlessness, and his disdain for the very emotions that rule him in his normal life. It was our first hint ever of the super villain we know will one day emerge.
The third is the final scene of the episode, when Lex visits Clark in the loft. There's an anvilicious conversation about best friends becoming enemies, but the good part is when Lex utters that portentous line, "Trust me, Clark. Our friendship is going to be the stuff of legend." It still gives me a thrill when I hear it!