This is simply what you think is the (not some of the, the) best example of any trope (an objective trope, not subjective, since this already is subjective). The "Crowning Example" if you will.
There could be several reasons you think an example is the best.
You think it's the best in terms of illustrating the trope.
You think it's the most well done.
It's your favorite play in that trope.
You just really like the source material.
Oh, several things before you list examples:
Each troper gets one example per trope, no more.
Don't go "no, this is," or phrases like that. This is about our own personal favorites.
The term "ad hominem". Find me one single instance of anybody ever using this term correctly, instead of just as a synonym for "insult" or "personal attack", and you'll deserve a medal for it. ~ ZuulMF
Meet the Spy; it's poignantly effective because it's also one of the few instances where the quip's deliverer has photographic evidence to backup the line! ~Pikawil, prescience, Jackpot, V Phantom, cosmictoast, Alloflifedecays, Dark, Paranoid Drone, syafati
Seconded. No other insult here is cruel enough to make a person die of dehydration...from crying. Telling it half way leaves them only crying for a week. ~ Waffletree
The Butterfly Effect. Not because it's the most unbelievable story, but because after he tells it she responds with "You're right, I don't believe you." ~ sinesofinsanity