The episode "Mr. Anderson's Balls", in which the boys go around a golf course, sneaking around and stealing golf balls (mainly Mr. Anderson's), and later selling them to the golf players (including Anderson himself), and they actually pull it off without a hitch. Such a rarity to see one of the boys' money-making schemes actually work to perfection.
And they sell them cheaper than the ones in the sports shop.
Tom Anderson gets one of his own after his neighbor threatens to sue him after Anderson's steamroller damaged his hedge, thanks to Beavis and Butt-Head in "Steamroller".
Bill: You're gonna pay for this, Anderson! Tom Anderson: Like hell I am. You're the one who told me to rent from Morgan's. Now get the hell out of my property you son of a bitch! [punches his neighbor, who falls to the ground] And if I ever see that damn dog of yours peeing on my yard again, I'm gonna shoot both of you!
Not to mention the scene where the duo rams a steamroller into Coach Buzzcut through a wall in the same episode.
In the episode "The Trial," Beavis and Butt-Head are on trial for egging Mr. Anderson's house, and defend themselves about as well as you'd expect...until Butt-Head is inspired by a thought-bubble of a celebrity he saw on TV, advising him to "Use the Force." Under the influence of this outside inspiration, Butt-Head promptly has x seconds of badass, an authoritve take-charge voice included:
Butt-Head: "Sir, so for all you know, it could have been—" *Points at Stewart, in the audience" "—HIM who threw rotten eggs at your window!"
Tom Anderson: "Well, all you kids DO look a lot alike..." *Adjusts his eyeglasses*
Butt-Head: "If that's your opinion, sir; then your testimony as an eyewitness is hardly credible!" *Points at Anderson* "It is incompetent, irrelevant, and immaterial!" *Promptly returns to normal, and sits down* "...Uh, or something. Uh huh huh. Uh huh huh huh huh. I rest on this guy's face....uhh, I mean I rest my case."
Granted, the mention of rotten eggs exposes that he and Beavis WERE the guilty party (since there no other references towards the eggs being rotten), but that doesn't detract from the sheer moment of awesome.
Beavis finally reaching his breaking point and telling Butt-head to shut up, followed by kicking him in the nads. Over a Bon Jovi video, of all things.
Stewart's Throw the Dog a Bone moment at the end of "Holy Cornholio". After putting up with Beavis and Butt Head's jokes, one of the series' Butt Monkeys is going to bang the women that Beavis and Butt Head pass up.