The Training Day parody with Wayne Brady, where he's revealed to be a dangerous sociopath — gunning down a guy with an AK-47, pimping, forcing Dave to smoke Angel Dust. It's funny even if you don't really get why it's so ironic (IE, if you don't know Wayne Brady).
Also, from the very first episode, the Clayton Bigsby sketch, especially its hilarious final line (just see it for yourself).
The moment when the leading voice of the white supremacist movement is revealed to be black to the public. The sheer mind bending-ness of the whole thing really hits home in that instant of dumbstruck silence. Especially when one of the members of the audience is simply unable to process it, and his head explodes.
Also also, the catchphrase-spawning Rick James episode, particularly the real Rick James' "justification" for his behavior: "Cocaine's a hell of a drug."
Also also also, the Racial Draft sketch, when the Asians draft the Wu Tang Clan: "Konichiwa, bitches!"
Basketball game. Charlie Murphy vs. Prince. And then come the pancakes...
Prince: (after scoring the final point) Game—blouses.
Silky Johnson shooting the slave master in the unused "Time Haters" skit was fucking hilarious.
Slave: But when's we gonna be free?!
Silky: That is a good question, my man. How about nowish? *BLAM*
The first time we met the Playa Haters:
Silky: Buck Nasty, what can I say about your suit that hasn't already been said about Afghanistan? It looks bombed out and depleted. As for you, Pitbull, very insulting what you said about my coat... it's made out of your mother's pubic hair. And the so-called Beautiful... why don't you click your heels together three times, and go back to Africa?
The "White People Can't Dance" skit, where they try and disprove the aforementioned notion. Dave having John Mayer play electric guitar in very professional and posh settings, and ?uestlove playing drums in a barber shop in Harlem.
Dave: (in a five-star restaurant) Play the one—the fight riff! Go! GO!
Chapelle imagines a world where the Internet is a real place.
(Dave walks by an Obstructive Bureaucrat and a roulette croupier) Bureaucrat: DEBT CONSOLIDATION! Dave: No. Croupier: Gambling~ Dave: No thanks. (A pop-up appears, repeating the scene) Bureaucrat: DEBT CONSOLIDATION! Dave: (annoyed grumble) Croupier: Gambling~ Dave: (more annoyed sounding snarl) (Another pop-up appears, repeating the scene) Dave: ''(shouting over Bureaucrat) "DEBT CONSOLIDATION"! NOOOO! God damn! Stop it with all the pop-ups!