In "For Now"; "Except for death and paying taxes, everything in life is only for now!"
All of "Mix Tape"; but especially Kate's little overjoyed "He likes me!" at the end.
The first time you watch it, 'Fantasies Come True' definitely counts as one of these, with Rod finally being able to admit that he's gay and discovering that Nicky, his roommate, best friend, and crush, likes him back. At least, right up until the end when it's revealed that Rod was just dreaming, one of the saddest moments in the entire show.
A meta example; the writers of the show have stated that they actually got letters from Gay Conservatives who stated how much they loved Rod as a character. The really heartwarming part, however, is the fact that Rod actually inspired some of them to come out of the closet in the first place! Just shows that even a fictional character can leave a positive impact on someone's life.