There's no way I could boil it down to just one (or two or ten) episode(s). I can pretty much find something fun and WAFFy in almost anything from the first and second seasons (with a few glaring exceptions).

But, gun to my head, I'd pick 'The Phoenix'. The whole Lex plot line is silly, but the romantic tension between our heroes makes up for it. It's the first time in the whole series where they're both able to acknowledge the attraction between them (and they're both ready to act on that attraction). If it's possible to wear out a DVD, I'm sure mine will stop working at the couch scene. I could watch that on an endless loop. <sigh>

Lois: You know, I have a funny feeling that you didn't tell me your biggest secret.

Clark: Well, just to put your little mind at ease, Lois, you're right.
Ides of Metropolis