Frisky Dingo/Funny

The longer any given conversation involving Xander Crewes goes, the more likely it is to reach Crowning Moment status, as his understanding of whatever's going on declines but his anger/confusion/excitement/whatever increases. His exchanges with Killface deserve special mention, particularly in season 2.
Almost the entire episode in which the Xtacles attempt to pass Nearl off as Xander Crews, with the highlight being either "Elephant showers with their noses!", "It's complicated enough without all the evil twin bullshit having," or the entire Flowers For Algernon/Harrison Bergeron/Tom Bergeron/Agamemnon exchange.
Late in Season 1, pretty much everyone (most notably Taquil and a group of extremely drunk Xtacles) end up in Chinatown watching a deathmatch. Their commentary is consistently hilarious, but special mention goes to Taquil's repeated proclamations of "Man, I love Chinatown!" or "I hate Chinatown!"
From the Season 1 finale: "My parents never established boundaries!"
Xander's "gray market safaris" and his claim of a mama panda bear being "the most dangerous game."
When Xander and Killface finale make it to the debate, poor Carter Hawkins (the moderator) is subjected to absolute chaos as the two of them try to orient themselves, with Xander shouting things like "Why does he get a spirit animal?!" and "I think my buzzer's broken!"
Near the end of Season 2, Wendel's digression on the morality of his plan: "We're dealing with some pretty profound ideologies here. You know, on the one hand, there's anti-abortion. On the other hand: Jengo! I've got a machete! Deal with it, Congress. You can't legislate morality. Although you can legislate machetes, turns out."
Master Cylinder!
Wendel's acid flashback to Lollapallooza.

Concert Goer: Are you feeling it, Wendel?
Wendel: Are you Jane's Addiction?
Concert Goer: Anubis has risen Wendel.
Wendel: Anubis has risen! That's not good!

In the first episode when Villain Protagonist Killface uses the severed torso of a twin he shot in a previous scene as a hand puppet as the other twin looks on and this quote:

Valerie: Please don't kill us!
Killface: Please don't make it so appealing!

- Second season episode where Xander's doctor gets confused by name of the (sorta) evil cyborg villainness:

Doctor: Well, that cracked your C3 and C4 vertebrae, so... you ever see Hooper?
Xander: Yeah, that robot with the big tits!
Doctor: No, but that sounds awesome.
Xander: It is!
Doctor: I meant the Burt Reynolds movie where he's a hard-living stuntman.
Xander: That sounds awesome.
Doctor: It is. Anyway, one more impact to the neck, and you'll be paralyzed.
Xander: My third-greatest fear!
Doctor: Same basic plot as in the movie.
Xander: God, that sounds awesome.
Doctor: It is.
Xander: But who's gonna stop Hooper?
Doctor: Well, it's already out on DVD.
Xander: No, I mean the robot with the big tits.
Doctor: Really sounds awesome.
Xander: It is.