"Hello. I'm Leonard Nimoy. The following tale of alien encounters is true. And by true, I mean false. It's all lies. But they're entertaining lies. And in the end, isn't that the real truth? The answer is...No."
Oh god that was inspired. Who would have thought that the best line in the X-Files episode would go to Spock?
There are many, many great lines in "You Only Move Twice" (Hank Scorpio may just be the best single-time character the Simpsons ever had), but I'll go with this line from Homer, regarding Tom Landry's Hat:
"Only management-type guys with big salaries like me can afford things like that - wait a minute, guys like me?
I'm a guy like me!"